System for deep denitrification by using biochemical effluent of sewage plant and control method thereof

Abstract

The invention belongs to the field of sewage treatment, and discloses a system for deep denitrification by using biochemical effluent of a sewage plant and a control method of the system. A grit chamber water outlet well of the system is connected with the PD reactor through a water pump and a flow meter, connected with the SAED reactor through the water pump and the flow meter and connected with the biochemical system through the flow meter, and the biochemical system is connected with the PD reactor through the flow meter and a nitrate nitrogen online detector. The PD reactor is connected with the middle tank through a water decanter, and the middle tank is connected with the SAED reactor through a water pump and a flow meter. An NH3-N online detector and a CODCr online detector are mounted on a water outlet well of the grit chamber; the middle tank is provided with a # imgabs0 # online detector; the PD reactor is provided with a bottom aeration system and a dissolved oxygen tester, and is connected with a blast pipe. The SAED reactor is provided with a submersible stirrer, a dissolved oxygen tester, a # imgabs1 # online detector and a CODCr online detector. On the premise of not additionally adding a carbon source, the total nitrogen removal rate of the system can be improved.

Description

Technical Field

[0001] The invention belongs to the field of sewage treatment and relates to a sewage deep denitrification system and a control method thereof. Background Art

[0002] With the continuous development of social economy, the emission standards of sewage treatment plants are becoming more and more stringent. Among them, the emission standard of TN (total nitrogen) has been generally increased from no more than 15 mg / L in the Level A standard of "Pollutant Emission Standard for Urban Sewage Treatment Plants" (GB18918-2002) to no more than 10 mg / L.

[0003] The AAO process is commonly used in the biochemical treatment section of sewage treatment plants. Because the C / N (carbon-nitrogen ratio) of the incoming water is low, a large amount of organic carbon source needs to be added to this section. In order to achieve the higher standard of TN not exceeding 10 mg / L, sewage treatment plants currently generally adopt the transformation measures of adding a denitrification filter and adding a carbon source to the filter, or the transformation measures of converting the AAO process into the AAOAO process and adding a carbon source to the second-stage A pool. These two transformation measures further increase the amount of added carbon source and increase the output of residual sludge, resulting in a substantial increase in the operating costs and carbon emissions of the sewage treatment plant.

[0004] The anaerobic ammonium oxidation (Anammox) process is a process that uses inorganic CO2 and CO 2-3 The process of oxidizing ammonia nitrogen into nitrogen gas using anaerobic ammonia oxidation as a carbon source and nitrite as an electron acceptor. This process is considered to be one of the most promising new denitrification processes because it does not require an organic carbon source and has the characteristics of low sludge production and high denitrification efficiency. However, since the nitrogen in the incoming water from the sewage treatment plant is mainly ammonia nitrogen and lacks nitrite nitrogen, it is technically difficult to control the biochemical oxidation stage of ammonia nitrogen to the nitrite stage (i.e. short-range nitrification), and it requires major changes to the existing biochemical process, so it is difficult to implement. Furthermore, a certain amount of nitrate nitrogen will be produced during the anaerobic ammonia oxidation reaction, and its theoretical denitrification rate is only 89%, and 11% of nitrate nitrogen cannot be eradicated. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a system for deep denitrification using biochemical effluent from a sewage plant and a control method thereof, so as to improve the total nitrogen removal rate of the system without adding an external carbon source.

[0006] The technical solution of the present invention is as follows: A system for deep denitrification using biochemical effluent from a sewage treatment plant comprises a grit chamber outlet well, a biochemical system, a PD reactor, an intermediate tank and a SAED reactor, wherein the grit chamber outlet well is connected to a first water inlet of the PD reactor through a No. 1 raw water pump and a No. 1 flow meter; the grit chamber outlet well is also connected to a first water inlet of the SAED reactor through a No. 2 raw water pump and a No. 2 flow meter; the grit chamber outlet well is also connected to a water inlet of the biochemical system through a No. 3 flow meter, and a water outlet of the biochemical system is connected to a second water inlet of the PD reactor through a No. 4 flow meter and a nitrate nitrogen online detector; the PD reactor is connected to a water inlet of the intermediate tank through a No. 1 decanter, and the intermediate tank is connected to a second water inlet of the SAED reactor through a SAED inlet pump and a No. 5 flow meter; the SAED reactor is provided with a No. 2 decanter; the grit chamber outlet well is installed with an NH3-N online detector and a No. 1 COD Cr Online detector; the middle tank is equipped with Online detector; PD reactor is equipped with bottom aeration system and No. 1 dissolved oxygen meter, and is connected to a blower through a blower pipe; SAED reactor is equipped with a submersible agitator, No. 2 dissolved oxygen meter, Online detector and No. 2 COD Cr Online detector.

[0007] Preferably, the PD reactor is provided with a fixed biological carrier filler for the attachment of short-range denitrifying microorganisms; the fixed biological carrier filler is made of polypropylene and polyethylene copolymer, and is appropriately modified for hydrophilicity, bioaffinity and charge, with a filling volume ratio of 20-30% and a specific surface area of ​​5600m 2 / m 3 .

[0008] Preferably, the SAED reactor is provided with a suspended bio-carrier filler made of HDPE with a specific surface area of ​​800 m 2 / m 3 , density 0.94~0.97kg / m 3 The filling volume ratio is 15~20%.

[0009] Preferably, a microbial carrier separation net is provided on the outlet weir of the No. 2 decanter to prevent the microbial carrier from flowing out.

[0010] The control method of the system for deep denitrification of biochemical effluent from a sewage plant controls the hydraulic retention time of the PD reactor between 45 and 65 minutes by adjusting the decanting height of the No. 4 flowmeter, the No. 1 flowmeter and the No. 1 decanter; and controls the hydraulic retention time of the PD reactor between 45 and 65 minutes by adjusting the No. 4 flowmeter, the nitrate nitrogen online detector, the No. 1 raw water pump, the No. 1 flowmeter and the No. 1 COD Cr Online detector controls COD in PD reactor Cr and The mass ratio of is between 1.5 and 2.5; combined with the detection mean value of the nitrate nitrogen online detector, the flow value of flow meter No. 1 and the flow value of flow meter No. 4 are controlled. Short-term denitrification The mass ratio of is controlled at more than 80%; and according to the detection mean value of the nitrate nitrogen online detector, the average hourly flow rate of flow meter No. 1, flow meter No. 2 and flow meter No. 4 is controlled, and the decanting height of decanter No. 1 is controlled to The ratio of concentration to NH3-N concentration was controlled in the range of 1.30~1.35.

[0011] Preferably, the SAED reactor is operated in a sequential batch mode, and each operation cycle is divided into stage one, stage two, stage three and stage four; Stage 1: When the submersible mixer is in working condition, the No. 2 raw water pump is turned on to pump raw water into the SAED reactor. After the raw water is pumped in, the No. 2 raw water pump is turned off and the submersible mixer is kept in working condition for another 50-70 minutes. Stage 2: First, start the SAED water inlet pump and submersible agitator, and the water temporarily stored in the intermediate tank enters the SAED reactor. After the water inlet is completed, the submersible agitator continues to operate until the end of this stage. The total time of this stage is 110~130min; Stage 3: Turn off the submersible mixer and keep it on for 25-35 minutes; Stage 4: Use the No. 2 decanter to discharge the supernatant from the SAED reactor to the deep treatment system.

[0012] Further preferably, the drainage ratio of stage 4 is controlled at 60-70%.

[0013] Preferably, the dissolved oxygen in the PD reactor is controlled between 0.1 and 0.5 by means of a No. 1 dissolved oxygen meter, a bottom aeration system and the blower.

[0014] Compared with the prior art, the present invention has the following characteristics: The present invention converts the nitrate nitrogen in the effluent of the secondary biochemical treatment of the sewage plant into nitrite through short-range denitrification (i.e. PD), and uses anaerobic ammonia oxidation coupled with endogenous denitrification (i.e. SAED) to treat the influent of the sewage plant to achieve the effect of deep denitrification. The principle is as follows: the external carbon source of the sewage plant is eliminated to further increase the concentration of nitrate nitrogen in the effluent of the biochemical system of the sewage plant; the effluent of the secondary biochemical treatment is adjusted and mixed with the water volume of the raw water, and the short-range denitrification process is used to use part of the organic matter in the raw water as the carbon source to convert the nitrate nitrogen in the effluent of the biochemical system of the sewage plant into nitrite nitrogen through short-range denitrification. The ratio of nitrite nitrogen to ammonia nitrogen produced by short-range denitrification is further adjusted with part of the raw water to meet the requirements of anaerobic ammonia oxidation (i.e. / NH3-N is maintained between 1.30 and 1.35), and the total nitrogen is efficiently removed by anaerobic ammonium oxidation reaction; at the same time, the endogenous denitrification process is coupled to completely remove the 11% nitrate nitrogen produced in the anaerobic ammonium oxidation reaction, and the total nitrogen removal rate of the system is increased to more than 95%.

[0015] After the existing biochemical system of the sewage treatment plant stops adding carbon sources, the ammonia nitrogen removal rate of its effluent remains basically unchanged, and can be maintained at about 99%, and the effluent concentration does not exceed 1 mg / L; due to insufficient carbon sources, its total nitrogen removal rate is reduced to about 33%, and the remaining total nitrogen, except for trace amounts of ammonia nitrogen, is all nitrate nitrogen, and its concentration reaches 40 mg / L. The present invention uses these nitrate nitrogen contained in the effluent as electron acceptors, and mixes them with raw water in an appropriate proportion, using the carbon source contained in the raw water as an electron donor, and short-range denitrification in the PD reactor to convert them into nitrite nitrogen ( ); then anaerobic ammonium oxidation reaction coupled with endogenous denitrification reaction occurs in the SAED reactor for deep denitrification.

[0016] The present invention utilizes the existing secondary biochemical effluent of the sewage treatment plant to provide nitrate nitrogen, thereby providing a stable supply of nitrate nitrogen substrate for short-range denitrification. Compared with short-range nitrification, short-range denitrification is easier to control, has looser environmental conditions, and is more likely to accumulate nitrite. Organic pollutants in raw water are used as carbon sources, and external carbon sources are eliminated, thereby reducing the cost of external carbon sources and the cost of sludge treatment and disposal. Nitrate nitrogen generated by the anaerobic ammonium oxidation reaction is completely removed, and the denitrification rate of a conventional anaerobic ammonium oxidation system is increased from 89% to more than 95%. When the present invention is applied to actual projects, there is basically no need to change the current process, and only new PD and SAED structures need to be added to properly distribute the incoming water from the sewage treatment plant. The technical transformation process can be seamlessly connected and is easier to achieve. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the working principle of the system embodiment of the present invention.

[0018] Description of reference numerals: 1. Water outlet well of sedimentation tank; 101. NH3-N online detector; 102. No. 1 COD Cr Online detector; 2. No. 1 raw water pump; 3. No. 1 flow meter; 4. PD reactor; 401. No. 1 decanter; 402. Bottom aeration system; 403. No. 1 dissolved oxygen meter; 404. Fixed biological carrier filler; 405. Blower pipe; 5. Intermediate tank; 501. Online detector; 6. SAED water inlet pump; 7. No. 5 flow meter; 8. No. 2 raw water pump; 9. No. 2 flow meter; 10. SAED reactor; 1001. No. 2 decanter; 1002. Submersible mixer; 1003. Suspended biological carrier filler; 1004. No. 2 dissolved oxygen meter; 1005. Online detector; 1006, No. 2 COD Cr Online detector; 11. Sand filter; 12. Chemical sedimentation tank; 13. Intermediate lift pump; 14. Lift pump room; 15. Biochemical system; 16. No. 3 flow meter; 17. Nitrate nitrogen online detector; 18. No. 4 flow meter. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with specific implementations and drawings.

[0020] In the present invention, the short-range denitrification reactor is referred to as a PD reactor 4. In the short-range denitrification reaction process, the organism provides an electron donor and the bacteria Restore to .

[0021] The present invention refers to the anaerobic ammonium oxidation coupled endogenous denitrification reactor as a SAED reactor 10. The anaerobic ammonium oxidation coupled endogenous denitrification (Synergistic Anammox Endogenous Denitrification) reaction refers to the anaerobic ammonium oxidation reaction and the endogenous denitrification reaction being coupled in one reactor, wherein the microorganisms first absorb organic matter into the body and convert it into an internal carbon source (PHAs); then the anaerobic ammonium oxidation reaction occurs, and the nitrite nitrogen and ammonia nitrogen are converted into nitrogen gas and a small amount of nitrate nitrogen; then the endogenous denitrification reaction occurs, and the microorganisms use the adsorbed internal carbon source to denitrify the nitrate nitrogen produced by the anaerobic ammonium oxidation reaction into nitrogen gas.

[0022] Take a water COD Cr The principle and application of the present invention are illustrated by taking a typical low carbon-nitrogen ratio sewage with a nitrogen concentration of 300 mg / L and an ammonia nitrogen concentration of 60 mg / L and a technical transformation example of a sewage plant using the commonly used AAO biochemical process + intermediate lift pump + chemical phosphorus removal, filtration and disinfection.

[0023] like Figure 1The overall system of this embodiment includes a grit chamber as a primary treatment system, a biochemical system 15 as a secondary treatment system, and a deep treatment system as a tertiary treatment system. The grit chamber is connected to a grit chamber outlet well 1, and the deep treatment system includes a lift pump room 14, which is connected to a chemical precipitation tank 12 through an intermediate lift pump 13, and the chemical precipitation tank 12 is connected to a sand filter tank 11. The grit chamber is generally a cyclone grit chamber or an aerated grit chamber. The overall system of this embodiment also includes a PD reactor 4, an intermediate tank 5, and a SAED reactor 10.

[0024] The water outlet well 1 of the grit chamber is equipped with an NH3-N online detector 101 and a No. 1 COD Cr Online detector 102.

[0025] The grit chamber outlet well 1 is connected to a No. 1 raw water pump 2 through a pipeline, and the No. 1 raw water pump 2 is connected to the first water inlet of the PD reactor 4 through a pipeline with a No. 1 flow meter 3. The grit chamber outlet well 1 is also connected to a No. 2 raw water pump 8 through a pipeline, and the No. 2 raw water pump 8 is connected to the first water inlet of the SAED reactor 10 through a pipeline with a No. 2 flow meter 9.

[0026] The No. 1 raw water pump 2 and the No. 1 flow meter 3 are used to measure and control the amount of raw water entering the PD reactor 4. The No. 2 raw water pump 8 and the No. 2 flow meter 9 are used to measure and control the amount of raw water entering the SAED reactor 10. The NH3-N online detector 101 and the No. 1 COD Cr The online detector 102 provides data for measuring and controlling the flow into the SAED reactor 10 and the PD reactor 4. Specifically, the SAED reactor 10 adjusts the flow of the No. 2 raw water pump 8 according to the data of the NH3-N online detector 101, and the PD reactor 4 adjusts the flow of the No. 1 COD Cr The data of the online detector 102 controls the flow of the No. 1 raw water pump 2.

[0027] The grit chamber outlet well 1 is also connected to the water inlet of the biochemical system 15 through a pipeline with a No. 3 flow meter 16, and the water outlet of the biochemical system 15 is connected to the second water inlet of the PD reactor 4 through a pipeline with a No. 4 flow meter 18 and a nitrate nitrogen online detector 17. The No. 4 flow meter 18 and the nitrate nitrogen online detector 17 are used to measure the amount of nitrate nitrogen entering the PD reactor 4.

[0028] The PD reactor 4 is provided with a first decanter 401, the discharge end of the first decanter 401 is connected to the water inlet of the intermediate tank 5, the intermediate tank 5 is connected to a SAED water inlet pump 6 through a pipeline, and the SAED water inlet pump 6 is connected to the second water inlet of the SAED reactor 10 through a pipeline with a fifth flow meter 7. The intermediate tank 5 is also provided with The function of the No. 5 flow meter 7 is to measure the water inflow of the SAED reactor 10 in each cycle, and the No. 5 flow meter 7 is used to calculate the water inflow of the SAED reactor 10 in each cycle. The amount.

[0029] The SAED reactor 10 is provided with a second decanter 1001 , and a discharge end of the second decanter 1001 is used to connect to the lift pump room 14 .

[0030] Further, the PD reactor 4 includes a PD reactor body of a reinforced concrete structure or a steel assembled structure, and the PD reactor body is equipped with external insulation measures, which can be a square tank body or a cylindrical water tank. The PD reactor body is connected to a blower pipe 405 for blowing air into the PD reactor 4 through a blower. A decanter 401 is provided in the PD reactor body to control the water level in the PD reactor 4, thereby controlling the hydraulic retention time (HRT), that is, the reaction time. A bottom aeration system 402 and a dissolved oxygen meter 403 are provided in the PD reactor body. The bottom aeration system 402 cooperates with the dissolved oxygen meter 403 to control the DO system in the PD reactor 4, and keep its dissolved oxygen in the range of 0.1~0.5mg / L. A braided fixed biological carrier filler 404 is provided in the PD reactor body for short-range denitrification microorganisms to attach. The PD reactor 4 is a coexistence system of biofilm + suspended sludge, and the fixed biological carrier filler 404 can greatly increase the concentration of microorganisms and improve the reaction efficiency. The fixed biological carrier filler 404 is made of polypropylene and polyethylene copolymer, and is modified with appropriate hydrophilicity, bio-affinity and charge (the filler is a product of Yixing Hengbo Environmental Protection). The filling volume ratio is 20~30%, the filler model is BZ50-S, and the specific surface area is 5600m 2 / m 3 .

[0031] The SAED reactor 10 includes a SAED reactor body of a reinforced concrete structure or a steel assembled structure. The SAED reactor body is equipped with external insulation measures and can be a square tank body or a cylindrical water tank. A No. 2 decanter 1001 is provided in the SAED reactor body, which is used to allow the SAED reactor 10 to operate intermittently. A microbial carrier partition is provided on the outlet weir of the No. 2 decanter 1001 to prevent the outflow of the microbial carrier. A submersible agitator 1002 is provided in the SAED reactor body to ensure that the microbial carrier in the SAED reactor 10 is in full contact with the sewage. A suspended biological carrier filler 1003 is provided in the SAED reactor body. The material is HDPE, which meets the standard of "High-density Polyethylene Suspended Carrier Filler for Water Treatment" (CJ / T461-2014), with a diameter of 25 mm and a specific surface area of ​​800 m 2 / m 3, density 0.94~0.97kg / m 3 The volume ratio of the filling is 15-20%. The SAED reactor body is provided with a No. 2 dissolved oxygen meter 1004 for detecting the dissolved oxygen inside the SAED reactor 10. Online detector 1005 and No. 2 COD Cr The online detector 1006 is used to detect the reaction end of the SAED reactor 10 Value and COD Cr concentration.

[0032] The following are examples of control methods.

[0033] The control method comprises: Control 1: PD reactor 4 adopts continuous operation mode, that is, continuous water inflow and continuous water outflow. The hydraulic retention time (HRT) of PD reactor 4 is controlled between 45 and 65 minutes by flow meter No. 4 18, flow meter No. 1 3 and decanter No. 1 401; the nitrate nitrogen online detector 17, raw water pump No. 1 2, flow meter No. 1 3 and COD No. 1 402 are used to control the hydraulic retention time (HRT) of PD reactor 4 between 45 and 65 minutes. Cr Online detector 102 controls COD in PD reactor 4 Cr / (mass ratio) is between 1.5 and 2.5; the dissolved oxygen in the PD reactor 4 is controlled between 0.1 and 0.5 by means of the No. 1 dissolved oxygen meter 403, the bottom aeration system 402 and the blower. Appropriate HRT, COD Cr / , DO is used to inhibit the further denitrification of nitrite nitrogen into nitrogen gas and increase the accumulation rate of nitrite nitrogen.

[0034] Control 2: Combine the detection mean of nitrate nitrogen online detector 17 to control the flow value of flow meter 1 3 and the flow value of flow meter 4 18. Short-term denitrification The quality ratio is controlled above 80%.

[0035] when Short-term denitrification When the mass ratio is greater than 60%, it indicates that the reaction system of the PD reactor 4 has been started. When the mass ratio reaches more than 80%, it indicates that the operation is normal.

[0036] Short-term denitrification The mass ratio of the PD reactor 4 is The mass ratio of the effluent from PD reactor 4 in one hour is Of which, the mass entering PD reactor 4 within one hour The quality calculation method is: multiply the flow value of the No. 4 flow meter 18 by the detection average value of the nitrate nitrogen online detector 17. The quality calculation method is: (the flow value of the No. 4 flow meter 18 + the flow value of the No. 1 flow meter 3) and The detection mean values ​​of the online detector 501 are multiplied.

[0037] Control 3: According to the detection mean value of the nitrate nitrogen online detector 17, control the average hourly flow rate of the No. 1 flow meter 3, the No. 2 flow meter 9 and the No. 4 flow meter 18, and control the decanting height of the No. 1 decanter 401. The ratio of concentration to NH3-N concentration was controlled in the range of 1.30~1.35.

[0038] For example, when the average flow rate of flow meter No. 4 18 is 100m 3 / h, when the value of nitrate nitrogen online detector 17 is 40mg / L, the raw water COD Cr If the concentration of water is 300mg / L, the water inlet flow rate of flow meter 3 should be controlled at 20~33.3m 3 / h, at this time, the COD of the influent of PD reactor 4 Cr / Between 2.0 and 2.5; the maximum total water inflow of PD reactor 4 is 133.3m 3 / h, the actual effective volume of the PD reactor 4 can be adjusted through the No. 1 decanter 401 to adjust the HRT to 45~65min. The short-range denitrification rate can reach more than 80%. Based on 80%, the effluent The concentration is: .

[0039] The production amount is 3200g / h, and the concentration of NH3-N introduced from the raw water is: .

[0040] / NH3-N is 24 / 15=1.6, which does not meet the requirement of being maintained between 1.30 and 1.35. The SAED reactor 10 needs to be re-adjusted with a certain amount of raw water to supplement ammonia nitrogen, that is, increase the water supply speed of the No. 2 raw water pump 8 and increase the value of the No. 2 flow meter 9. The ratio of the concentration to the NH3-N concentration was adjusted to between 1.30 and 1.35.

[0041] Control 4: Control each operation cycle of the SAED reactor 10 into four stages.

[0042] The SAED reactor 10 adopts a sequential batch operation (sequential batch operation is derived from the "Outdoor Drainage Design Standard" GB50014), and operates six cycles per day, each cycle running for six hours. Each operation cycle is divided into stage one, stage two, stage three and stage four.

[0043] Stage 1: When the submersible mixer 1002 is in working condition, the No. 2 raw water pump 8 is turned on to pump raw water into the SAED reactor 10. After the raw water is pumped in, the No. 2 raw water pump 8 is turned off, and the submersible mixer 1002 is kept in working condition for another 50 to 70 minutes.

[0044] Specifically in this example, the No. 2 raw water pump 8 and the submersible mixer 1002 are started to pump an appropriate amount (3.5% of the volume of the SAED reactor 10). The raw water inflow per cycle is 28.3m 3 , the effective volume of SAED reactor 10 is (533.3+28.3) / 0.7=802m 3 , the raw water with a ratio of 3.5%) is pumped into the SAED reactor 10 (in this example: flow rate 85.2m 3 / h, duration 20min, water inflow 28.3m 3 ), the microorganisms retained in the previous cycle of the SAED reactor 10 are fully in contact with the raw water under the stirring and mixing of the submersible mixer 1002. The SAED reactor 10 is not aerated and is in an anaerobic state. S (denitrifying glycogenotrophic bacteria) and DPAO S (Denitrifying polyphosphate bacteria) absorb organic carbon sources and convert them into PHA S And stored in the microorganisms, after the raw water intake is completed, turn off the No. 2 raw water pump 8. The submersible mixer 1002 is maintained in the working state for another 60 minutes before entering the second stage.

[0045] The main function of stage 1 is to take in water and undergo organic carbon source adsorption and conversion reactions, further replenishing ammonia nitrogen. / NH3-N is kept in an appropriate range.

[0046] Phase 2: First, start the SAED water inlet pump 6 and the submersible mixer 1002, and the water temporarily stored in the intermediate tank 5 enters the SAED reactor 10. After the water inlet is completed, the submersible mixer 1002 continues to operate until the end of this phase, and the total time of this phase is 110-130 minutes.

[0047] Specifically in this example, the SAED inlet pump 6 and the submersible mixer 1002 are first started, and the inlet flow rate is 1066m 3 / h, and then shut down SAED water inlet pump 6 (water inlet volume 533.3m 3), the submersible agitator 1002 continues to operate. / NH3-N is kept in an appropriate range. The total time of this stage is 120 minutes.

[0048] The first 60 minutes of stage 2 is mainly anaerobic ammonium oxidation reaction, that is, anaerobic ammonium oxidizing bacteria convert nitrite nitrogen and ammonia nitrogen into nitrogen gas, and generate 11% nitrate nitrogen at the same time. The biochemical reaction can be expressed as follows: .

[0049] After 60minDGAO S and DPAO S PHA stored in the body S The nitrate nitrogen produced by anaerobic ammonium oxidation is denitrified into nitrogen gas, thereby achieving the purpose of deep denitrification. The second stage mainly involves anaerobic ammonium oxidation reaction and endogenous denitrification reaction, which is the core reaction stage of the SAED reactor 10.

[0050] In stage 2, the water pumped by SAED inlet pump 6 contains The amount is 24mg / L×533.3m 3 (m 3 ) = 12800 g (24 mg / L comes from the formula 01), the amount of NH3-N is 15 mg / L × 533.3 m 3 =8000g (15mg / L comes from formula 02); the amount of NH3-N in the raw water pumped in by the No. 2 raw water pump 8 in stage 1 is 60mg / L×28.3m 3 = 1698 g. Therefore, it can be proved that the SAED reactor only needs to pump a small amount of raw water to / NH3-N is adjusted to 1.32, which reduces the difficulty of control and enters COD Cr The amount is small and is used by endogenous denitrification, which can avoid the COD Cr High problem.

[0051] Stage 3: Turn off the submersible mixer 1002 and keep it on for 25 to 35 minutes.

[0052] This stage is the sedimentation stage. The submersible agitator 1002 is turned off, and mud and water separation occurs in the SAED reactor 10. The suspended sludge settles to the bottom of the SAED reactor 10. The suspended biological carrier filler 1003 also partially settles due to the growth of a large amount of biofilm. After 30 minutes of sedimentation, the SAED reactor 10 enters stage 4.

[0053] Stage 4: The supernatant is discharged from the SAED reactor 10 to the deep treatment system using the second decanter 1001. The drainage ratio is controlled at 60-70%.

[0054] Specifically in this example, the drainage time is 30 minutes and the drainage ratio is 70% (the drainage ratio refers to the ratio of the water inflow or drainage volume in each cycle to the total effective volume of the reactor. For example, the water inflow of SAED reactor 10 in this example is 533.3+28.3=561.6 per cycle, so the total effective volume of SAED is 561.6÷0.7=802m 3 , the drainage volume of each cycle is 802×0.7=561.6, which means the drainage ratio is 70%).

[0055] This stage is the drainage stage. The second decanter 1001 discharges the supernatant from the SAED reactor 10, and the suspended biological carrier filler 1003 is blocked by the screen of the second decanter 1001 and retained in the SAED reactor 10. The discharged supernatant enters the deep treatment system of the sewage plant (generally known as the chemical phosphorus removal, filtration and disinfection system of the lifting pump room, which is an existing system of the sewage plant).

[0056] The DO of the effluent of PD reactor 4 is below 0.5mg / L. Therefore, after entering the raw water in stage 1, a small amount of DO will be consumed by microorganisms, and the dissolved oxygen meter 1004 No. 2 should be below 0.1mg / L, which means that there is no DO. The data of the online detector 1005 experienced a process of slowly rising in the first 60 minutes and then slowly falling in the next 60 minutes. The highest value appeared at around 60 minutes, showing data of about 4.5 mg / L (12800×0.26 / [1.32×(28.3+533.3)]). At this time, the total nitrogen removal rate of the system has reached 92.5% ((60-4.5) / 60). In the next 60 minutes, due to the endogenous denitrification reaction, The nitrogen will be further denitrified. The data displayed by the online detector 1005 will continue to decrease, the concentrations of residual ammonia nitrogen, nitrate nitrogen, etc. will not exceed 3 mg / L, and the total nitrogen removal rate will reach 95%.

[0057] From this example, it can be seen that the water from the sewage treatment plant is divided into three parts. Based on the calculation of one cycle of the SAED reactor 10, the amount of water pumped into the intermediate tank 5 in one cycle is 533.3m 3 , water inlet from biochemical system 15 400m 3 (counted as the first portion), 133m of water is taken in from No. 1 raw water pump 2 3 (counted as the second point); the raw water entering from the No. 2 raw water pump 8 is 28.3m 3 (counted as the third batch), the total processing volume of one cycle is 561.6m 3 Of these, only 400m 3It needs to pass through the existing biochemical system 15 of the sewage plant, accounting for 71.2%, and the remaining 28.8% directly enters the PD reactor 4 or SAED reactor 10, without consuming a large amount of air to oxidize organic matter and nitrate ammonia nitrogen, so the energy consumption of the blower of the sewage plant will be greatly reduced. At the same time, since no external carbon source is added, the sludge production rate of the SAED reactor 10 and the PD reactor 4 is very low, and the overall biochemical system sludge production rate of the system will be reduced by at least 60%, which also greatly reduces the cost of sludge treatment and disposal.

Claims

1. A system for deep denitrification using biochemical effluent from a sewage treatment plant, comprising a grit chamber effluent well (1), a biochemical system (15), a PD reactor (4), an intermediate tank (5) and a SAED reactor (10), characterized in that: The grit chamber outlet well (1) is connected to the first water inlet of the PD reactor (4) through a No. 1 raw water pump (2) and a No. 1 flow meter (3); the grit chamber outlet well (1) is also connected to the first water inlet of the SAED reactor (10) through a No. 2 raw water pump (8) and a No. 2 flow meter (9); the grit chamber outlet well (1) is also connected to the water inlet of the biochemical system (15) through a No. 3 flow meter (16); the water outlet of the biochemical system (15) is connected to the water inlet of the biochemical system (15) through a No. 4 flow meter (18) and a nitrate nitrogen online detector. The detector (17) is connected to the second water inlet of the PD reactor (4); the PD reactor (4) is connected to the water inlet of the intermediate tank (5) through the first decanter (401); the intermediate tank (5) is connected to the second water inlet of the SAED reactor (10) through the SAED water inlet pump (6) and the fifth flow meter (7); the SAED reactor (10) is provided with a second decanter (1001); the sedimentation tank outlet well (1) is equipped with an NH3-N online detector (101) and a first COD Cr Online detector (102); the middle tank (5) is provided with The PD reactor (4) is provided with a bottom aeration system (402) and a No. 1 dissolved oxygen meter (403), and is connected to a blower through a blower pipe (405); the SAED reactor (10) is provided with a submersible agitator (1002), a No. 2 dissolved oxygen meter (1004), Online detector (1005) and No. 2 COD Cr Online detector (1006).

2. The system for deep denitrification using biochemical effluent from a sewage plant as claimed in claim 1, characterized in that: The PD reactor (4) is provided with a fixed biological carrier filler (404) for short-range denitrifying microorganisms to attach; the fixed biological carrier filler (404) is made of polypropylene and polyethylene copolymer, and is appropriately modified in terms of hydrophilicity, bio-affinity and charge, with a filling volume ratio of 20-30% and a specific surface area of ​​5600m 2 / m 3 .

3. The system for deep denitrification using biochemical effluent from a sewage plant as claimed in claim 1, characterized in that: The SAED reactor (10) is provided with a suspended biological carrier filler (1003) made of HDPE with a specific surface area of ​​800 m 2 / m 3 , density 0.94~0.97kg / m 3 The filling volume ratio is 15~20%.

4. The system for deep denitrification using biochemical effluent from a sewage plant as claimed in claim 1, characterized in that: A microbial carrier separation net is provided on the outlet weir of the No. 2 decanter (1001) to prevent the microbial carrier from flowing out.

5. The control method of the system for deep denitrification using biochemical effluent from a sewage plant according to any one of claims 1 to 4, characterized in that: The hydraulic retention time of the PD reactor (4) is controlled between 45 and 65 minutes by adjusting the decanting height of the No. 4 flow meter (18), the No. 1 flow meter (3) and the No. 1 decanter (401); the No. 4 flow meter (18), the nitrate nitrogen online detector (17), the No. 1 raw water pump (2), the No. 1 flow meter (3) and the No. 1 COD Cr The online detector (102) controls the COD in the PD reactor (4) Cr and The mass ratio is between 1.5 and 2.5; and combined with the detection mean value of the nitrate nitrogen online detector (17), the flow value of the No. 1 flow meter (3) and the flow value of the No. 4 flow meter (18) are controlled, and the Short-term denitrification The mass ratio of is controlled to be above 80%; and according to the detection mean value of the nitrate nitrogen online detector (17), the average hourly flow rate of the No. 1 flow meter (3), the No. 2 flow meter (9) and the No. 4 flow meter (18) is controlled, and the decanting height of the No. 1 decanter (401) is controlled to The ratio of concentration to NH3-N concentration was controlled in the range of 1.30~1.

35.

6. The control method of the system for deep denitrification using biochemical effluent from a sewage plant as claimed in claim 5, characterized in that: The SAED reactor (10) is operated in a sequential batch mode, and each operation cycle is divided into stage 1, stage 2, stage 3 and stage 4; Stage 1: When the submersible mixer (1002) is in working condition, the No. 2 raw water pump (8) is turned on to pump raw water into the SAED reactor (10). After the raw water is pumped in, the No. 2 raw water pump (8) is turned off, and the submersible mixer (1002) is kept in working condition for another 50 to 70 minutes; Phase 2: First, the SAED water inlet pump (6) and the submersible mixer (1002) are started, and the water temporarily stored in the intermediate tank (5) enters the SAED reactor (10). After the water inlet is completed, the submersible mixer (1002) continues to operate until the end of this phase. The total time of this phase is 110-130 minutes; Stage 3: Turn off the submersible mixer (1002) and keep it on for 25-35 minutes; Stage 4: Use the No. 2 decanter (1001) to discharge the supernatant from the SAED reactor (10) to the deep treatment system.

7. The control method of the system for deep denitrification using biochemical effluent from a sewage plant as claimed in claim 6, characterized in that: The drainage ratio in stage 4 is controlled at 60~70%.

8. The control method of the system for deep denitrification using biochemical effluent from a sewage plant as claimed in claim 5, characterized in that: The dissolved oxygen in the PD reactor (4) is controlled between 0.1 and 0.5 by means of a No. 1 dissolved oxygen meter (403), a bottom aeration system (402) and the blower.

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