A highly efficient denitrification AO wastewater treatment equipment and process

Abstract

The invention discloses an AO sewage treatment device and process with high-efficiency denitrification, belonging to the technical field of sewage treatment. The AO sewage treatment device consists of five parts: a hydrolysis acidification tank, an anoxic reaction tank, an aerobic reaction tank, a sedimentation tank, and an external power supply; the anode electrode is a modified platinum mesh electrode; the preparation method of the modified platinum mesh electrode consists of the following steps: preparing modified small-particle graphite powder, preparing modified large-particle graphite powder, coating once, and coating twice; the AO sewage treatment device and process of the invention can save costs and shorten the acclimation time while realizing high-efficiency denitrification and COD removal, and at the same time, it also has the advantages of long equipment service life and strong impact resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to an AO sewage treatment device and process with high-efficiency denitrification. Background Art

[0002] AO process is the anoxic aerobic process, a denitrification process widely used in sewage treatment. It mainly consists of two parts: a front anoxic denitrification reactor and a rear aerobic nitrification reactor. This process has a good removal effect on COD and total nitrogen. Its denitrification principle is: the nitrification liquid in the nitrification reactor is refluxed to the denitrification reactor, and the denitrification bacteria in the denitrification reactor use the organic matter in the raw water as a carbon source and the oxygen of the nitrate in the reflux liquid as an electron acceptor to carry out respiration and life activities, and reduce nitrate nitrogen to nitrogen gas, that is, denitrification. The denitrification process consumes a large amount of carbon source, and often requires artificial addition of BOD, which increases costs.

[0003] The hydrolysis acidification tank can convert insoluble organic matter in wastewater into soluble organic matter, decompose macromolecular organic matter into small molecular organic matter, and improve the biodegradability of wastewater. At the same time, the hydrolysis acidification tank can still ensure the effluent quality when the influent COD is high, and can improve the sewage treatment system's ability to resist shock loads. Therefore, in sewage treatment, the hydrolysis acidification tank is often connected in series with the AO process in order to achieve a stable and effective treatment effect, but this scheme has the problem of low mass transfer efficiency between the two phases, resulting in a long acclimatization time and difficulty in efficient denitrification and COD removal.

[0004] Electrolysis is an electrochemical wastewater treatment process suitable for the treatment of heavy metal ions and toxic and difficult-to-biodegrade organic pollutants. By placing plates in the electrolytic cell and applying electricity to generate a potential difference between the plates, pollutants in the wastewater undergo oxidation reactions at the anode, reduction reactions at the cathode, or react with electrolysis products, thereby being harmlessly removed. However, the electrolytic cells in conventional electrolysis methods have problems such as limited plate life and poor water stability. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides an AO sewage treatment equipment and process with high-efficiency denitrification, which can save costs and shorten the acclimatization time while achieving high-efficiency denitrification and COD removal. At the same time, it also has the advantages of long equipment service life and strong impact resistance.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] An AO sewage treatment equipment with high efficiency denitrification, which consists of five parts: hydrolysis acidification tank, anoxic reaction tank, aerobic reaction tank, sedimentation tank, and external power supply;

[0008] The external power supply is connected to the variable resistor, the anode electrode, and the cathode electrode;

[0009] The hydrolysis acidification tank is equipped with a filter screen, which is located at 7 / 8 of the height of the hydrolysis acidification tank;

[0010] The hydrolysis acidification tank is provided with a first stirring device, and the anoxic reaction tank is provided with a second stirring device;

[0011] The aerobic reaction tank is provided with an aeration device;

[0012] The sedimentation tank is equipped with a mud discharge pipe, a reflector, a water inlet channel and a central pipe;

[0013] The sedimentation tank is connected to the anoxic reaction tank via a first circulation pump, and the aerobic reaction tank is connected to the anoxic reaction tank via a second circulation pump;

[0014] Gravity flow can be carried out between the hydrolysis acidification tank and the anoxic reaction tank;

[0015] The anode electrode is a modified platinum mesh electrode;

[0016] The cathode electrode is a platinum mesh electrode with a length of 4.5 cm, a width of 0.1 cm, and a height of 4.5 cm;

[0017] The volume ratio of the hydrolysis acidification tank, the anoxic reaction tank, and the aerobic reaction tank is 1-1.1:1-1.1:2;

[0018] The preparation method of the modified platinum mesh electrode comprises the following steps: preparing modified small-particle graphite powder, preparing modified large-particle graphite powder, coating once, and coating twice;

[0019] The modified small-particle graphite powder is prepared by mixing small-particle graphite powder, polyethylene glycol 2000 and water, stirring at room temperature, controlling the stirring speed to be 100-400 rpm, stirring time to be 50-60 min, centrifuging, taking the precipitate, washing it with deionized water, drying it, and then mixing it with ethylenediaminetetraacetic acid, ball milling at room temperature, controlling the ball-to-material ratio to be 5-6:1, the rotation speed to be 300-350 rpm, and the ball milling time to be 30-40 min, to obtain the modified small-particle graphite powder;

[0020] In the preparation of the modified small-particle graphite powder, the mass volume ratio of the small-particle graphite powder, polyethylene glycol 2000, water, and ethylenediaminetetraacetic acid is 90-100 g: 14-16 g: 800-1000 mL: 6-6.5 g;

[0021] The D50 particle size of the small-particle graphite powder is 1 μm;

[0022] The modified large-particle graphite powder is prepared by mixing large-particle graphite powder, trisodium citrate and water, stirring at room temperature, controlling the stirring speed to be 100-400 rpm, stirring time to be 50-60 min, centrifuging, taking precipitate, washing with deionized water, drying, and then mixing with anhydrous magnesium chloride, ball milling at room temperature, controlling the ball-to-material ratio to be 5-6:1, the rotation speed to be 300-350 rpm, and the ball milling time to be 70-80 min, to obtain the modified large-particle graphite powder;

[0023] In the preparation of the modified large-particle graphite powder, the mass volume ratio of the large-particle graphite powder, trisodium citrate, water, and anhydrous magnesium chloride is 90-100g:17-20g:800-1000mL:9-10g;

[0024] The D50 particle size of the large-particle graphite powder is 10 μm;

[0025] The primary coating comprises mixing polyvinyl pyrrolidone, sodium carboxymethyl starch and water, stirring at 45-50° C., controlling the stirring speed to be 200-400 rpm, stirring for 30-40 min, adding modified small-particle graphite powder and acetylene black, and continuing stirring for 60-80 min to obtain a primary coating slurry, and then uniformly coating the primary coating slurry on the surface of the platinum mesh electrode, and vacuum drying after the coating to obtain a platinum mesh electrode after the primary coating;

[0026] In the one-time coating, the mass ratio of polyvinyl pyrrolidone, sodium carboxymethyl starch and water is 2-2.2:5.2-5.5:50;

[0027] The mass ratio of modified small-particle graphite powder, acetylene black, and polyvinyl pyrrolidone added in the early stage is 30-35:11-12:2-2.2;

[0028] The D50 particle size of the acetylene black is 40 nm;

[0029] The platinum mesh electrode is 4.5 cm long, 0.1 cm wide and 4.5 cm high;

[0030] When the primary coating slurry is uniformly coated on the surface of the platinum mesh electrode, the coating thickness is 140-160 μm;

[0031] The secondary coating comprises mixing polyvinyl pyrrolidone, sodium carboxymethyl starch and water, stirring at 45-50° C., controlling the stirring speed to be 200-400 rpm, stirring for 30-40 min, adding modified large-particle graphite powder and acetylene black, and continuing to stir for 60-80 min to obtain a secondary coating slurry, and then uniformly coating the secondary coating slurry on the surface of the platinum mesh electrode, and vacuum drying after coating to obtain a modified platinum mesh electrode;

[0032] In the secondary coating, the mass ratio of polyvinyl pyrrolidone, sodium carboxymethyl starch and water is 2-2.2:5.2-5.5:50;

[0033] The mass ratio of modified large-particle graphite powder, acetylene black and polyvinyl pyrrolidone is 36-40:5-6:2-2.2;

[0034] The D50 particle size of the acetylene black is 40 nm;

[0035] When the secondary coating slurry is uniformly coated on the surface of the platinum mesh electrode, the coating thickness is 160-180 μm;

[0036] A process for treating sewage using the aforementioned AO sewage treatment equipment, comprising the following steps: cultivating anaerobic sludge, acclimatizing the sludge, and operating stably;

[0037] The anaerobic sludge is cultured by culturing the sludge in the aerobic tank of the sewage treatment plant to obtain the anaerobic sludge;

[0038] In the anaerobic sludge culture, glucose is used as the carbon source, COD is controlled to be 250-350 mg / L, the stirring speed is 60-100 r / min, and the culture time is 20-40 min;

[0039] The sludge is domesticated, anaerobic sludge is inoculated to the bottom of the hydrolysis acidification tank, the liquid level of the sludge bed is controlled to 1 / 3 of the height of the hydrolysis acidification tank, and the anaerobic sludge is inoculated to the anoxic reaction tank and the aerobic reaction tank, the aerobic reaction tank is aerated until the dissolved oxygen content of the aerobic reaction tank is maintained at more than 2 mg / L, an external power supply is turned on, and a variable resistor is adjusted, a first simulated wastewater containing trace elements is continuously introduced, and then the first simulated wastewater containing trace elements is stopped, and a second simulated wastewater containing trace elements is continuously introduced until the domestication is completed;

[0040] In the acclimated sludge, the rotation speed of the first stirring device in the hydrolysis acidification tank is 70-80r / min;

[0041] The inoculation amount of the anaerobic sludge in the anoxic reaction tank and the aerobic reaction tank is 4500-5500 mg / L;

[0042] The rotation speed of the second stirring device in the anoxic reaction tank is 70-90r / min;

[0043] The voltage of the external power supply is 1.9-2.1V, and the resistance of the variable resistor is 1.9-2.1MΩ;

[0044] When the first simulated wastewater containing trace elements is continuously introduced, the volume ratio of the continuous water inflow of the first simulated wastewater containing trace elements, the nitrification liquid return flow, and the sludge return flow is 1-1.1:2:1-1.1, and the organic loading rate is 0.4-0.5 kgCOD / (m 3 ·d) The continuous flow time is 5-6 days;

[0045] The first simulated wastewater containing trace elements has a glucose content of 780-820 mg / L, an NH4Cl content of 19-21 mg / L, a KH2PO4 content of 1.9-2.1 mg / L, a MnCl2•4H2O content of 1.9-2.1 mg / L, a CaCl2 content of 1.9-2.1 mg / L, a FeCl3 content of 0.9-1.1 mg / L, a ZnCl2•4H2O content of 0.9-1.1 mg / L, and a MgCl2•6H2O content of 0.9-1.1 mg / L;

[0046] The injection rate of the first simulated wastewater containing trace elements is n / 800 mL / min, wherein n is the volume of the hydrolysis acidification tank in mL;

[0047] The second simulated wastewater containing trace elements has a glucose content of 1950-2050 mg / L, a NH4Cl content of 79-81 mg / L, a KH2PO4 content of 9-11 mg / L, a MnCl2•4H2O content of 1.9-2.1 mg / L, a CaCl2 content of 1.9-2.1 mg / L, a FeCl3 content of 0.9-1.1 mg / L, a ZnCl2•4H2O content of 0.9-1.1 mg / L, and a MgCl2•6H2O content of 0.9-1.1 mg / L;

[0048] The injection rate of the second simulated wastewater containing trace elements is n / 600 mL / min, wherein n is the volume of the hydrolysis acidification tank in mL;

[0049] When the second simulated wastewater containing trace elements is continuously introduced, the organic loading rate is 1.4-1.6 kg COD / (m 3 ·d) The continuous flow time is 5-6 days;

[0050] During acclimatization, the pH of the hydrolysis acidification tank was maintained at 5.8-6.8, and the pH of the anoxic reaction tank and the aerobic reaction tank was maintained at 6.5-8.5;

[0051] The stable operation is to adjust the pH of the wastewater to 6.3-6.7, pass it into the hydrolysis acidification tank, and then turn on the external power supply, the effluent of the hydrolysis acidification tank flows into the anoxic reaction tank, the effluent of the anoxic reaction tank flows into the aerobic reaction tank, and the nitrification liquid in the aerobic reaction tank flows back to the anoxic reaction tank for denitrification, and the nitrification liquid reflux ratio is 250-350%, until the effluent is stable;

[0052] In the stable operation, the voltage of the external power supply is 1.9-2.1V, and the resistance of the variable resistor is 1-2MΩ;

[0053] The temperature of the anoxic reaction tank is 18-22° C., the rotation speed of the second stirring device in the anoxic reaction tank is 70-90 r / min, and the dissolved oxygen in the anoxic reaction tank is 0.48-0.52 mg / L;

[0054] The temperature of the hydrolysis acidification tank is 33-37°C, and the speed of the first stirring device in the hydrolysis acidification tank is 70-80r / min;

[0055] The hydraulic retention time HRT of the hydrolysis acidification tank and the anoxic reaction tank is 5-10h, and the hydraulic retention time HRT of the aerobic reaction tank is 10-20h;

[0056] The temperature of the aerobic reaction tank is 18-22° C., and the dissolved oxygen is 1.9-2.1 mg / L.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] (1) The AO sewage treatment equipment and process with high efficiency denitrification of the present invention can combine the advantages of electrolysis and biochemical treatment processes by coupling low-voltage electrolysis with a biochemical treatment process, thereby solving the problem of low mass transfer efficiency between the two phases in the biochemical treatment process and improving the sewage treatment efficiency, and can also save energy consumption for electrolysis and extend the life of the electrode. In addition, by combining the electrolysis and biochemical treatment processes, the electrons generated in the hydrolysis acidification tank pass through the circuit into the anoxic reaction tank, providing energy for denitrification and reducing the consumption of carbon sources in the anoxic reaction tank, thereby saving costs and reducing the requirements of the treatment system for the B / C ratio of sewage, reducing the need for artificial addition of carbon sources, and reducing the cost of sewage treatment; and the external power supply improves the denitrification capacity of the system, and the system reaction rate is controlled by the resistance value of the external variable resistor, so that the system has strong adaptability to changes in the influent load and strong impact resistance. Moreover, by detecting the voltage across the external resistor, the electron transfer activity between the fermentation bacteria can be intuitively observed, which plays an important role in screening electron-interactive bacteria.

[0059] (2) The AO sewage treatment equipment and process with high efficiency denitrification of the present invention uses a modified platinum mesh electrode as the anode electrode. The modification process of the platinum mesh electrode is a process of coating the platinum mesh electrode with modified small-particle graphite powder and modified large-particle graphite powder respectively, wherein the surface of the modified small-particle graphite powder is coated with ethylenediaminetetraacetic acid, which can chelate metal ions and form a small-pore coating layer on the surface of the platinum mesh electrode; the surface of the modified large-particle graphite powder is coated with a complex of trisodium citrate and magnesium ions, which can form a coordination bond with glucose and form a large-pore coating layer on the surface of the platinum mesh electrode, thereby enriching bacteria, metal ions and glucose on the surface of the modified platinum mesh electrode, thereby shortening the domestication time and improving the domestication efficiency. During the enrichment, the metal ions are located in the sub-outer layer and the glucose is located in the outermost layer. By adsorbing the metal ions and glucose separately, the loss of the metal ions and glucose is avoided, and competitive adsorption caused by large differences in adsorption capacity when the same adsorption carrier is used for adsorption can also be avoided;

[0060] (3) The AO sewage treatment equipment and process with high-efficiency denitrification of the present invention can achieve high-efficiency denitrification and COD removal. For simulated acidified wastewater with a glucose content of 3000 mg / L, an NH4Cl content of 100 mg / L, a KH2PO4 content of 20 mg / L, a MnCl2•4H2O content of 2 mg / L, a CaCl2 content of 2 mg / L, a FeCl3 content of 1 mg / L, a ZnCl2•4H2O content of 1 mg / L, and a MgCl2•6H2O content of 1 mg / L, after continuous operation for 6 days, the system effluent was stable, the ammonia nitrogen content in the system effluent was 8.6 mg / L, the nitrate nitrogen content was 1.2 mg / L, and the COD removal rate of the system was 94%;

[0061] (4) The AO sewage treatment equipment and process with high efficiency denitrification of the present invention can shorten the acclimatization time. During the acclimatization, the first simulated wastewater containing trace elements is continuously introduced for 5 days, and then the second simulated wastewater containing trace elements is continuously introduced for 5 days to complete the acclimatization. The COD in the effluent of the system is stabilized at 100 mg / L, and the total nitrogen is stabilized at 8 mg / L.

[0062] (5) The AO sewage treatment equipment and process for high-efficiency nitrogen removal of the present invention have the advantage of strong impact resistance and still have a good removal effect on high ammonia nitrogen wastewater. For simulated acidified wastewater with a glucose content of 3000 mg / L, an NH4Cl content of 250 mg / L, a KH2PO4 content of 20 mg / L, a MnCl2•4H2O content of 2 mg / L, a CaCl2 content of 2 mg / L, a FeCl3 content of 1 mg / L, a ZnCl2•4H2O content of 1 mg / L, and a MgCl2•6H2O content of 1 mg / L, after continuous operation for 8 days, the system effluent was stable, the ammonia nitrogen content in the system effluent was 29.5 mg / L, the nitrate nitrogen content was 3.2 mg / L, and the COD removal rate of the system was 91%. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 Schematic diagram of AO equipment for efficient nitrogen removal;

[0064] In the figure: 1-hydrolysis acidification tank; 2-anoxic reaction tank; 3-aerobic reaction tank; 4-sedimentation tank; 5-first stirring device; 6-second stirring device; 7-anode electrode; 8-cathode electrode; 9-external power supply; 10-variable resistor; 11-aeration device; 12-first circulation pump; 13-second circulation pump; 14-sludge discharge pipe; 15-reflection plate; 16-water inlet channel; 17-center pipe; 18-filter. DETAILED DESCRIPTION

[0065] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described.

[0066] Example 1

[0067] like Figure 1As shown, an AO sewage treatment equipment with high efficiency denitrification is composed of five parts: a hydrolysis acidification tank 1, an anoxic reaction tank 2, an aerobic reaction tank 3, a sedimentation tank 4, and an external power supply 9. The external power supply 9 is connected to a variable resistor 10, an anode electrode 7, and a cathode electrode 8. The anode electrode 7 is a modified platinum mesh electrode, and the cathode electrode 8 is a platinum mesh electrode with a length of 4.5 cm, a width of 0.1 cm, and a height of 4.5 cm. The volume ratio of the hydrolysis acidification tank 1, the anoxic reaction tank 2, and the aerobic reaction tank 3 is 1:1:2; a filter screen 18 is installed in the hydrolysis acidification tank 1, and the position of the filter screen 18 is located at 7 of the hydrolysis acidification tank 1. / 8 high, can play the role of intercepting sludge; the hydrolysis acidification tank 1 is provided with a first stirring device 5; the anoxic reaction tank 2 is provided with a second stirring device 6; the aerobic reaction tank 3 is provided with an aeration device 11; the sedimentation tank 4 is equipped with a sludge discharge pipe 14, a reflector 15, a water inlet channel 16, and a central pipe 17; the sedimentation tank 4 is connected to the anoxic reaction tank 2 through a first circulation pump 12, and the first circulation pump 12 is used for sludge return; the aerobic reaction tank 3 is connected to the anoxic reaction tank 2 through a second circulation pump 13, and the second circulation pump 13 is used for digestion liquid return; the hydrolysis acidification tank 1 and the anoxic reaction tank 2 can be self-flowing;

[0068] The preparation method of the modified platinum mesh electrode is:

[0069] 1. Preparation of modified small-particle graphite powder: 95 g of small-particle graphite powder, 15 g of polyethylene glycol 2000, and 900 mL of water were mixed, stirred at room temperature, the stirring speed was controlled to be 300 rpm, the stirring time was 55 min, centrifuged, the precipitate was taken, washed with deionized water, dried, and then mixed with 6.2 g of ethylenediaminetetraacetic acid, and ball milled at room temperature, the ball-to-material ratio during ball milling was controlled to be 5:1, the rotation speed was 320 rpm, and the ball milling time was 35 min to obtain modified small-particle graphite powder;

[0070] The D50 particle size of the small-particle graphite powder is 1 μm;

[0071] 2. Preparation of modified large-particle graphite powder: 95 g of large-particle graphite powder, 18 g of trisodium citrate, and 900 mL of water were mixed, stirred at room temperature, the stirring speed was controlled to be 300 rpm, the stirring time was 55 min, centrifuged, the precipitate was taken, washed with deionized water, dried, and then mixed with 9.5 g of anhydrous magnesium chloride, and ball milled at room temperature, the ball-to-material ratio during ball milling was controlled to be 5:1, the rotation speed was 300 rpm, and the ball milling time was 75 min to obtain modified large-particle graphite powder;

[0072] The D50 particle size of the large-particle graphite powder is 10 μm;

[0073] 3. Primary coating: polyvinyl pyrrolidone, sodium carboxymethyl starch and water are mixed in a mass ratio of 2.1:5.4:50, stirred at 45°C, the stirring speed is controlled to be 300rpm, the stirring time is 35min, modified small-particle graphite powder and acetylene black are added, and the mass ratio of modified small-particle graphite powder, acetylene black and polyvinyl pyrrolidone added in the early stage is controlled to be 32:12:2.1, and stirring is continued for 70min to obtain a primary coating slurry, and then the primary coating slurry is evenly coated on the surface of the platinum mesh electrode, the coating thickness is controlled to be 150μm, and vacuum drying is performed after the coating is completed to obtain a platinum mesh electrode after the primary coating;

[0074] The D50 particle size of the acetylene black is 40 nm;

[0075] The platinum mesh electrode is 4.5 cm long, 0.1 cm wide and 4.5 cm high;

[0076] 4. Secondary coating: polyvinyl pyrrolidone, sodium carboxymethyl starch and water are mixed in a mass ratio of 2.1:5.4:50, stirred at 45°C, the stirring speed is controlled to be 300rpm, the stirring time is 35min, modified large-particle graphite powder and acetylene black are added, and the mass ratio of modified large-particle graphite powder, acetylene black and polyvinyl pyrrolidone added in the early stage is controlled to be 38:5.5:2.1, and stirring is continued for 70min to obtain a secondary coating slurry, and then the secondary coating slurry is evenly coated on the surface of the platinum mesh electrode, and the coating thickness is controlled to be 170μm. After coating, vacuum drying is performed to obtain a modified platinum mesh electrode;

[0077] The D50 particle size of the acetylene black is 40 nm;

[0078] This embodiment also provides a process for treating sewage using the aforementioned AO sewage treatment equipment, specifically:

[0079] 1. Cultivate anaerobic sludge: Cultivate the sludge from the aerobic pool of the sewage treatment plant, use glucose as the carbon source, control the COD to 300 mg / L, and stir at 80 r / min. After 30 minutes of cultivation, the cultivation ends and anaerobic sludge is obtained;

[0080] The volatile suspended solids (VSS) content of the anaerobic sludge is 3%;

[0081] 2. Sludge acclimation: inoculate anaerobic sludge to the bottom of hydrolysis and acidification tank 1 to form a sludge bed, control the liquid level of the sludge bed to 1 / 3 of the height of hydrolysis and acidification tank 1, control the speed of the first stirring device 5 in hydrolysis and acidification tank 1 to 75r / min, and inoculate anaerobic sludge to anoxic reaction tank 2 and aerobic reaction tank 3, control the inoculation amount to 5000mg / L, control the speed of the second stirring device 6 in anoxic reaction tank 2 to 80r / min, and inoculate the aerobic reaction tank 3. Aeration, through aeration, the dissolved oxygen content of the aerobic reaction tank 3 is maintained at more than 2 mg / L, the external power supply 9 is turned on for acclimation, the voltage of the external power supply 9 is controlled to 2V, and the resistance of the variable resistor 10 is adjusted to the middle value of 2MΩ. During the acclimation process, the first simulated wastewater containing trace elements is continuously introduced, and the volume ratio of the continuous water inflow of the first simulated wastewater containing trace elements, the nitrification liquid return flow, and the sludge return flow is controlled to be 1:2:1, and the organic load rate is 0.45 kg COD / (m 3 ·d), after 5 days of continuous flow, the first simulated wastewater containing trace elements was stopped, and the second simulated wastewater containing trace elements was started, and the organic load rate was controlled to be 1.5 kg COD / (m 3 ·d) After 5 days of continuous aeration, the acclimatization was completed, the COD in the effluent of the system was stabilized at 100 mg / L, and the total nitrogen was stabilized at 8 mg / L;

[0082] The first simulated wastewater containing trace elements has a glucose content of 800 mg / L, an NH4Cl content of 20 mg / L, a KH2PO4 content of 2 mg / L, a MnCl2•4H2O content of 2 mg / L, a CaCl2 content of 2 mg / L, a FeCl3 content of 1 mg / L, a ZnCl2•4H2O content of 1 mg / L, and a MgCl2•6H2O content of 1 mg / L;

[0083] The injection rate of the first simulated wastewater containing trace elements is n / 800 mL / min, wherein n is the volume of the hydrolysis acidification tank in mL;

[0084] The second simulated wastewater containing trace elements has a glucose content of 2000 mg / L, an NH4Cl content of 80 mg / L, a KH2PO4 content of 10 mg / L, a MnCl2•4H2O content of 2 mg / L, a CaCl2 content of 2 mg / L, a FeCl3 content of 1 mg / L, a ZnCl2•4H2O content of 1 mg / L, and a MgCl2•6H2O content of 1 mg / L;

[0085] The injection rate of the second simulated wastewater containing trace elements is n / 600 mL / min, wherein n is the volume of the hydrolysis acidification tank in mL;

[0086] During acclimatization, the pH of the hydrolysis acidification tank 1 was maintained at 5.8-6.8, and the pH of the anoxic reaction tank 2 and the aerobic reaction tank 3 were maintained at 6.5-8.5;

[0087] 3. Stable operation: adjust the pH of the simulated acidified wastewater to 6.5, introduce the simulated acidified wastewater into the hydrolysis acidification tank 1, then turn on the external power supply 9, control the voltage of the external power supply 9 to 2V, and adjust the resistance of the variable resistor 10 to the middle value of 2MΩ. During the operation, control the temperature of the anoxic reaction tank 2 to 20°C, the speed of the second stirring device 6 in the anoxic reaction tank 2 to 80r / min, control the dissolved oxygen in the anoxic reaction tank 2 to 0.5mg / L, the temperature of the hydrolysis acidification tank 1 to 35°C, the speed of the first stirring device 5 in the hydrolysis acidification tank 1 to 75r / min, and control the hydraulic retention time HRT of the hydrolysis acidification tank 1 and the anoxic reaction tank 2 to 6h , the hydraulic retention time HRT of aerobic reaction tank 3 is controlled to 12h. During the operation, the macromolecular organic matter in the hydrolysis acidification tank is converted into small molecules, and electrons are generated at the same time; the effluent of hydrolysis acidification tank 1 flows into anoxic reaction tank 2, and the effluent of anoxic reaction tank 2 flows into aerobic reaction tank 3. The temperature of aerobic reaction tank 3 is controlled to 20℃, and the dissolved oxygen is controlled to 2mg / L; during the operation, the COD removal rate of anoxic reaction tank 2 is 20% on the first day of operation, and stabilizes to 35% on the sixth day. The nitrification process is completed in aerobic reaction tank 3, and ammonia nitrogen is converted into nitrate nitrogen. The COD removal rate of aerobic reaction tank 3 is 70% on the first day of operation, and stabilizes to 92% on the sixth day. The nitrified liquid in the aerobic reaction tank 3 is returned to the anoxic reaction tank 2 for denitrification. The nitrified liquid return ratio is 250%. The electrons generated by the hydrolysis acidification tank 1 and the protons coupled with the electrons flow into the anoxic reaction tank 2 through the electrodes, providing energy for the denitrification in the anoxic reaction tank. The denitrifying bacteria use the electrons generated by the degradation of COD and the electrons flowing in through the circuit to provide energy for the denitrification reaction, converting the nitrate nitrogen in the nitrified liquid flowing into the anoxic reaction tank 2 into nitrogen gas, completing the denitrification process. After 6 days of continuous operation, the system effluent was stable, the content of ammonia nitrogen in the system effluent was 8.6 mg / L, the content of nitrate nitrogen was 1.2 mg / L, and the COD removal rate of the system was 94%;

[0088] The simulated acidified wastewater contains 3000 mg / L of glucose, 100 mg / L of NH4Cl, 20 mg / L of KH2PO4, 2 mg / L of MnCl2•4H2O, 2 mg / L of CaCl2, 1 mg / L of FeCl3, 1 mg / L of ZnCl2•4H2O, and 1 mg / L of MgCl2•6H2O.

[0089] The flow rate of the simulated acidified wastewater is n0 / 6m 3 / h, where n0 is the volume of the hydrolysis acidification tank in m 3 .

[0090] Example 2

[0091] On the basis of Example 1, in the second step of acclimating the sludge, "the liquid level of the sludge bed is controlled to 1 / 3 of the height of the hydrolysis acidification tank 1" is changed to "the liquid level of the sludge bed is controlled to 1 / 4 of the height of the hydrolysis acidification tank 1"; "and the anaerobic sludge is inoculated into the anoxic reaction tank 2 and the aerobic reaction tank 3, and the inoculation amount is controlled to be 5000 mg / L" is changed to "and the anaerobic sludge is inoculated into the anoxic reaction tank 2 and the aerobic reaction tank 3, and the inoculation amount is controlled to be 3000 mg / L"; the continuous passage time after the first simulated wastewater containing trace elements is passed is changed from 5 days to 7 days;

[0092] After the acclimation was completed, the COD in the system effluent was stabilized at 110 mg / L and the total nitrogen was stabilized at 8.3 mg / L.

[0093] This example illustrates that lowering the liquid level of the sludge bed and reducing the inoculum amount of anaerobic sludge will lead to a longer acclimatization time, indicating that the liquid level of the sludge bed and the inoculum amount of anaerobic sludge in Example 1 are both optimal values.

[0094] Example 3

[0095] On the basis of Example 1, the content of NH4Cl in the simulated easily acidified wastewater introduced in the third step of stable operation was changed from 100 mg / L to 250 mg / L; the reflux ratio of the nitrifying solution was changed from 250% to 350%; the hydraulic retention time HRT of the hydrolysis acidification tank 1 and the anoxic reaction tank 2 was changed from 6 h to 10 h, and the hydraulic retention time HRT of the aerobic reaction tank 3 was changed from 12 h to 20; the resistance value of the variable resistor 10 was adjusted from 2 MΩ to 1 MΩ; after 8 days of continuous operation, the system effluent was stable, the content of ammonia nitrogen in the system effluent was 29.5 mg / L, the content of nitrate nitrogen was 3.2 mg / L, and the COD removal rate of the system was 91%.

[0096] This example illustrates that for wastewater with high ammonia nitrogen content, better treatment results can still be obtained after increasing the reflow ratio and lengthening the hydraulic retention time HRT.

[0097] Example 4

[0098] On the basis of Example 1, a platinum mesh electrode with a length of 4.5 cm, a width of 0.1 cm, and a height of 4.5 cm is used instead of the modified platinum mesh electrode as the anode electrode 7, that is, the platinum mesh electrode is not subjected to primary coating and secondary coating;

[0099] According to the acclimation method of Example 1, after continuously passing the second simulated wastewater containing trace elements for 5 days, the COD in the system effluent was 154.2 mg / L and the total nitrogen was 10.7 mg / L. After continuing to continuously pass the second simulated wastewater containing trace elements for 2 days, the COD in the system effluent was stabilized at 104.1 mg / L and the total nitrogen was stabilized at 8.1 mg / L.

[0100] This embodiment illustrates that the acclimation time can be shortened and the acclimation efficiency can be improved after the platinum mesh electrode used as the anode electrode 7 is modified.

[0101] Unless otherwise specified, all percentages used in the present invention are by mass.

[0102] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An AO sewage treatment equipment with high efficiency denitrification, characterized in that: The method comprises five parts: a hydrolysis acidification tank (1), an anoxic reaction tank (2), an aerobic reaction tank (3), a sedimentation tank (4), and an external power supply (9); The external power source (9) is connected to the variable resistor (10), the anode electrode (7), and the cathode electrode (8); The anode electrode (7) is a modified platinum mesh electrode; The preparation method of the modified platinum mesh electrode comprises the following steps: preparing modified small-particle graphite powder, preparing modified large-particle graphite powder, coating once, and coating twice; The modified small-particle graphite powder is prepared by mixing small-particle graphite powder, polyethylene glycol 2000 and water, stirring at room temperature, centrifuging, taking a precipitate, washing it, drying it, and then mixing it with ethylenediaminetetraacetic acid, and ball milling it at room temperature to obtain the modified small-particle graphite powder; The modified large-particle graphite powder is prepared by mixing the large-particle graphite powder, trisodium citrate and water, stirring at room temperature, centrifuging, taking the precipitate, washing it, drying it, and then mixing it with anhydrous magnesium chloride, and ball milling it at room temperature to obtain the modified large-particle graphite powder; The primary coating comprises mixing polyvinyl pyrrolidone, sodium carboxymethyl starch and water, stirring at 45-50° C., adding modified small-particle graphite powder and acetylene black, and continuing to stir to obtain a primary coating slurry, and then uniformly coating the primary coating slurry on the surface of the platinum mesh electrode, and vacuum drying after the coating to obtain a platinum mesh electrode after the primary coating; The secondary coating comprises mixing polyvinyl pyrrolidone, sodium carboxymethyl starch and water, stirring at 45-50° C., adding modified large-particle graphite powder and acetylene black, and continuing to stir to obtain a secondary coating slurry, and then uniformly coating the secondary coating slurry on the surface of the platinum mesh electrode after the primary coating, and vacuum drying after the coating is completed to obtain a modified platinum mesh electrode; The hydrolysis acidification tank (1) is provided with a filter screen (18), and the filter screen (18) is located at 7 / 8 of the height of the hydrolysis acidification tank (1); The hydrolysis acidification tank (1) is provided with a first stirring device (5) and an anode electrode (7), and the anoxic reaction tank (2) is provided with a second stirring device (6) and a cathode electrode (8); The aerobic reaction tank (3) is provided with an aeration device (11); The sedimentation tank (4) is equipped with a mud discharge pipe (14), a reflector (15), a water inlet channel (16), and a central pipe (17); The sedimentation tank (4) is connected to the anoxic reaction tank (2) via a first circulation pump (12), and the aerobic reaction tank (3) is connected to the anoxic reaction tank (2) via a second circulation pump (13); The hydrolysis acidification tank (1) and the anoxic reaction tank (2) are capable of self-flow; The cathode electrode (8) is a platinum mesh electrode with a length of 4.5 cm, a width of 0.1 cm and a height of 4.5 cm; The volume ratio of the hydrolysis acidification tank (1), the anoxic reaction tank (2), and the aerobic reaction tank (3) is 1-1.1:1-1.1:

2.

2. The AO sewage treatment equipment with high efficiency denitrification according to claim 1 is characterized in that: In the preparation of the modified small-particle graphite powder, the mass volume ratio of the small-particle graphite powder, polyethylene glycol 2000, water, and ethylenediaminetetraacetic acid is 90-100 g: 14-16 g: 800-1000 mL: 6-6.5 g; The D50 particle size of the small-particle graphite powder is 1 μm.

3. The AO sewage treatment equipment with high efficiency denitrification according to claim 1 is characterized in that: In the preparation of the modified large-particle graphite powder, the mass volume ratio of the large-particle graphite powder, trisodium citrate, water, and anhydrous magnesium chloride is 90-100g:17-20g:800-1000mL:9-10g; The D50 particle size of the large-particle graphite powder is 10 μm.

4. The AO sewage treatment equipment with high efficiency denitrification according to claim 1 is characterized in that: In the one-time coating, the mass ratio of polyvinyl pyrrolidone, sodium carboxymethyl starch and water is 2-2.2:5.2-5.5:50; The mass ratio of modified small-particle graphite powder, acetylene black, and polyvinyl pyrrolidone added in the early stage is 30-35:11-12:2-2.2; The D50 particle size of the acetylene black is 40 nm; The platinum mesh electrode is 4.5 cm long, 0.1 cm wide and 4.5 cm high; When the primary coating slurry is uniformly coated on the surface of the platinum mesh electrode, the coating thickness is 140-160 μm.

5. The AO sewage treatment equipment with high efficiency denitrification according to claim 1 is characterized in that: In the secondary coating, the mass ratio of polyvinyl pyrrolidone, sodium carboxymethyl starch and water is 2-2.2:5.2-5.5:50; The mass ratio of modified large-particle graphite powder, acetylene black and polyvinyl pyrrolidone is 36-40:5-6:2-2.2; The D50 particle size of the acetylene black is 40 nm; When the secondary coating slurry is uniformly coated on the surface of the platinum mesh electrode, the coating thickness is 160-180 μm.

6. A process for treating sewage using the sewage treatment equipment according to any one of claims 1 to 5, characterized in that: The process consists of the following steps: cultivating anaerobic sludge, acclimatizing the sludge, and stabilizing operation.

7. The process for treating sewage according to claim 6, characterized in that: The anaerobic sludge is cultured by culturing the sludge in the aerobic tank of the sewage treatment plant to obtain the anaerobic sludge; In the cultured anaerobic sludge, glucose is used as the carbon source, COD is controlled to be 250-350 mg / L, the stirring speed is 60-100 r / min, and the culture time is 20-40 min.

8. The process for treating sewage according to claim 6, characterized in that: The sludge acclimation comprises inoculating anaerobic sludge to the bottom of the hydrolysis and acidification tank (1), controlling the liquid level of the sludge bed to 1 / 3 of the height of the hydrolysis and acidification tank (1), inoculating anaerobic sludge to the anoxic reaction tank (2) and the aerobic reaction tank (3), aerating the aerobic reaction tank (3) until the dissolved oxygen content of the aerobic reaction tank (3) is maintained at more than 2 mg / L, turning on the external power supply (9), adjusting the variable resistor (10), continuously introducing the first simulated wastewater containing trace elements, then stopping the introduction of the first simulated wastewater containing trace elements, and continuously introducing the second simulated wastewater containing trace elements until the acclimation is completed; In the acclimated sludge, the rotation speed of the first stirring device (5) in the hydrolysis acidification tank (1) is 70-80 r / min; The inoculation amount of the anaerobic sludge in the anoxic reaction tank (2) and the aerobic reaction tank (3) is 4500-5500 mg / L; The rotation speed of the second stirring device (6) in the anoxic reaction tank (2) is 70-90 r / min; The voltage of the external power supply (9) is 1.9-2.1V, and the resistance of the variable resistor (10) is 1.9-2.1MΩ; When the first simulated wastewater containing trace elements is continuously introduced, the volume ratio of the continuous water inflow of the first simulated wastewater containing trace elements, the nitrification liquid return flow, and the sludge return flow is 1-1.1:2:1-1.1, and the organic loading rate is 0.4-0.5 kgCOD / (m 3 ·d) The continuous flow time is 5-6 days; The first simulated wastewater containing trace elements has a glucose content of 780-820 mg / L, an NH4Cl content of 19-21 mg / L, a KH2PO4 content of 1.9-2.1 mg / L, a MnCl2•4H2O content of 1.9-2.1 mg / L, a CaCl2 content of 1.9-2.1 mg / L, a FeCl3 content of 0.9-1.1 mg / L, a ZnCl2•4H2O content of 0.9-1.1 mg / L, and a MgCl2•6H2O content of 0.9-1.1 mg / L; The injection rate of the first simulated wastewater containing trace elements is mL / min, where n is the volume of the hydrolysis acidification tank (1), in mL; The second simulated wastewater containing trace elements has a glucose content of 1950-2050 mg / L, a NH4Cl content of 79-81 mg / L, a KH2PO4 content of 9-11 mg / L, a MnCl2•4H2O content of 1.9-2.1 mg / L, a CaCl2 content of 1.9-2.1 mg / L, a FeCl3 content of 0.9-1.1 mg / L, a ZnCl2•4H2O content of 0.9-1.1 mg / L, and a MgCl2•6H2O content of 0.9-1.1 mg / L; The injection rate of the second simulated wastewater containing trace elements is mL / min, where n is the volume of the hydrolysis acidification tank (1), in mL; When the second simulated wastewater containing trace elements is continuously introduced, the organic loading rate is 1.4-1.6 kg COD / (m 3 ·d) The continuous flow time is 5-6 days; During acclimatization, the pH of the hydrolysis acidification tank (1) was maintained at 5.8-6.8, and the pH of the anoxic reaction tank (2) and the aerobic reaction tank (3) were maintained at 6.5-8.

5.

9. The process for treating sewage according to claim 6, characterized in that: In the stable operation, the pH of the wastewater is adjusted to 6.3-6.7, and the wastewater is introduced into the hydrolysis acidification tank (1). Then, the external power supply (9) is turned on, and the effluent of the hydrolysis acidification tank (1) flows into the anoxic reaction tank (2). The effluent of the anoxic reaction tank (2) flows into the aerobic reaction tank (3). The nitrified liquid in the aerobic reaction tank (3) flows back to the anoxic reaction tank (2) for denitrification. The nitrified liquid reflux ratio is 250-350%, until the effluent is stable. During the stable operation, the voltage of the external power supply (9) is 1.9-2.1V, and the resistance of the variable resistor (10) is 1-2MΩ; The temperature of the anoxic reaction tank (2) is 18-22° C., the rotation speed of the second stirring device (6) in the anoxic reaction tank (2) is 70-90 r / min, and the dissolved oxygen in the anoxic reaction tank (2) is 0.48-0.52 mg / L; The temperature of the hydrolysis acidification tank (1) is 33-37° C., and the rotation speed of the first stirring device (5) in the hydrolysis acidification tank (1) is 70-80 r / min; The hydraulic retention time HRT of the hydrolysis acidification tank (1) and the anoxic reaction tank (2) is 5-10 hours, and the hydraulic retention time HRT of the aerobic reaction tank (3) is 10-20 hours; The temperature of the aerobic reaction tank (3) is 18-22°C, and the dissolved oxygen is 1.9-2.1 mg / L.

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