CN117509882A - Predictive accurate aeration method - Google Patents
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- 238000000034 method Methods 0.000 title claims abstract description 34
- 238000005273 aeration Methods 0.000 title claims abstract description 29
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 105
- 239000010865 sewage Substances 0.000 claims abstract description 31
- 238000012544 monitoring process Methods 0.000 claims abstract description 25
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 11
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 11
- 239000011574 phosphorus Substances 0.000 claims abstract description 11
- 238000004062 sedimentation Methods 0.000 claims abstract description 11
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 claims abstract description 7
- 238000004364 calculation method Methods 0.000 claims abstract description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 67
- 229910052760 oxygen Inorganic materials 0.000 claims description 67
- 239000001301 oxygen Substances 0.000 claims description 67
- 238000006243 chemical reaction Methods 0.000 claims description 54
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 32
- 238000013461 design Methods 0.000 claims description 21
- 229910052757 nitrogen Inorganic materials 0.000 claims description 16
- 238000005259 measurement Methods 0.000 claims description 12
- 229910052799 carbon Inorganic materials 0.000 claims description 7
- 230000001186 cumulative effect Effects 0.000 claims description 7
- MMDJDBSEMBIJBB-UHFFFAOYSA-N [O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[NH6+3] Chemical compound [O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[NH6+3] MMDJDBSEMBIJBB-UHFFFAOYSA-N 0.000 claims description 6
- 238000005070 sampling Methods 0.000 claims description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 5
- 230000001580 bacterial effect Effects 0.000 claims description 3
- 239000003575 carbonaceous material Substances 0.000 claims description 3
- 238000007599 discharging Methods 0.000 claims description 3
- 230000002906 microbiologic effect Effects 0.000 claims description 3
- 244000005700 microbiome Species 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 238000007619 statistical method Methods 0.000 claims description 3
- 230000001590 oxidative effect Effects 0.000 claims description 2
- 238000005265 energy consumption Methods 0.000 abstract description 6
- 238000004134 energy conservation Methods 0.000 abstract description 2
- 239000011651 chromium Substances 0.000 description 25
- 238000009792 diffusion process Methods 0.000 description 8
- 230000005540 biological transmission Effects 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- 238000010992 reflux Methods 0.000 description 4
- 229920006395 saturated elastomer Polymers 0.000 description 4
- 239000010802 sludge Substances 0.000 description 4
- 238000012546 transfer Methods 0.000 description 4
- 230000001276 controlling effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000009825 accumulation Methods 0.000 description 2
- 238000012937 correction Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000029087 digestion Effects 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000036284 oxygen consumption Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000002798 spectrophotometry method Methods 0.000 description 2
- 238000005276 aerator Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 150000001844 chromium Chemical class 0.000 description 1
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- 238000005516 engineering process Methods 0.000 description 1
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- 238000006396 nitration reaction Methods 0.000 description 1
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Classifications
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- G—PHYSICS
- G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
- G16C—COMPUTATIONAL CHEMISTRY; CHEMOINFORMATICS; COMPUTATIONAL MATERIALS SCIENCE
- G16C20/00—Chemoinformatics, i.e. ICT specially adapted for the handling of physicochemical or structural data of chemical particles, elements, compounds or mixtures
- G16C20/10—Analysis or design of chemical reactions, syntheses or processes
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/006—Regulation methods for biological treatment
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/30—Aerobic and anaerobic processes
- C02F3/302—Nitrification and denitrification treatment
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/08—Chemical Oxygen Demand [COD]; Biological Oxygen Demand [BOD]
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/14—NH3-N
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/16—Total nitrogen (tkN-N)
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/10—Biological treatment of water, waste water, or sewage
Abstract
The invention belongs to the field of sewage treatment, and discloses a predictive accurate aeration method, which comprises the following steps: inflow COD according to real-time on-line monitoring Cr Real-time calculation of theoretical air demand G by using ammonia nitrogen, TN values and designed effluent quality index values s The method comprises the steps of carrying out a first treatment on the surface of the By G s ×K Anan (safety) As t Stagnation of food Air supply quantity G of fan set after moment s-control An instruction; the feedback auxiliary control system feeds back the DO value of the tail end of the aerobic tank in real time, and the DO minimum value is set as DO min To prevent the secondary sedimentation tank from generating anaerobic phosphorus release, if DO value is larger than DO min The system is not adjusted and continues to run to the new G s-control After calculation, adjusting; if DO value is less than DO min The air supply amount G is increased as required s increase Is increased until the DO concentration of the aerobic tank exceeds DO min Stopping at a certain rate (e.g. 10%). The invention takes feedforward as main and DO feedback as auxiliary, which can ensure the quality of effluent water and realize energy conservation and consumption reduction.
Description
Technical Field
The invention relates to the field of sewage treatment, in particular to a predictive accurate aeration method.
Background
The activated sludge process is one of the most basic and core methods for sewage treatment, has a development history of hundreds of years, and has been widely used worldwide. Aeration is usually the most dominant energy consumption of the activated sludge process (related research shows that aeration occupies 50-70% of the total energy consumption of a sewage treatment plant) and is also the main source of indirect carbon emission of the sewage treatment plant. Therefore, aeration becomes a key point of research on the optimal operation of sewage treatment plants.
The consumption of oxygen in biological cells is mainly determined by two aspects: BOD (BOD) 5 Removing the required oxygen consumption; second is NH 3 The oxygen consumption required for N nitration is achieved in an aerobic tank. In addition, in theory, the denitrification process in the anoxic tank also generates a part of dissolved oxygen, so that the oxygen demand of the aeration system can be reduced.
In practice, stable operation of the biological system is typically achieved by controlling the DO concentration at the outlet of the aerobic tank ("feed-back"), as shown in FIG. 1. The DO concentration at the outlet of the aerobic tank is controlled to be about 2.0mg/L, when the DO value is less than 1.8mg/L, the DO concentration of the aerobic tank is increased by increasing the air supply quantity of the aeration system in a frequency conversion or starting-up fan quantity increasing mode, when the DO value is more than 2.5mg/L, the DO concentration of the aerobic tank is decreased by decreasing the air supply quantity of the aeration system in a frequency conversion or starting-up fan quantity reducing mode, and the relative stability of the DO value of the aerobic tank is realized by the mode.
The basic logic of the method is that: when the inflow is normal, the whole biological treatment system is relatively stable as long as DO of the system is ensured to be stable, and the quality of the effluent is ensured. However, there is a large difference between the actual condition and the design condition, and the actual inlet water quality generally fluctuates at any time and is far lower than the design inlet water quality. This will have a versatile impact, mainly expressed in the following aspects:
(1) The actual oxygen demand will be significantly lower than the design value.
The design is usually carried out according to the probability water inlet concentration of 90-95%, the design is a relatively conservative fixed value, the actual value is fluctuating, and most of the time is less than the design value. In addition, from the national practical situation, the actual BOD of the incoming water is due to the low efficiency of the sewage collection system 5 The concentration is well below the design value, which means that the actual oxygen demand of the biochemical system will be significantly below the design value. Therefore, the DO value is fixed at about 2.0mg/L according to the design value in the running process, which is practically uneconomical, and the DO concentration is not required to be maintained at about 2.0mg/L in the actual running process.
(2) The buffering capacity of the system to DO is weak, and DO value is difficult to control.
Because the actual inflow water quality is far lower than the designed inflow water quality, the DO consumption capacity of the whole biological system is weaker than the design value, meanwhile, the DO stabilization capacity is also weaker, the air supply capacity of the air supply system is stronger, the situation of 'big malar trolley' is unavoidable, so that the DO value is continuously high and cannot be controlled in many sewage treatment plants, and the system energy consumption is higher.
(3) The DO value of the internal and external reflux is higher, and the normal operation of the front anoxic tank and the anaerobic tank is influenced.
Because the system has weaker DO consumption capability and slower consumption rate, the system has higher DO concentration no matter in-reflux or out-reflux, and the reaction environment of the front anoxic tank and the anaerobic tank is inevitably influenced, so that the denitrification and the anaerobic phosphorus release of the system are influenced, and the high-efficiency operation of the biological system is not facilitated.
The analysis shows that the actual situation is much more complex than the design working condition, and the traditional 'feedback' control method taking DO concentration as a control target has certain limitation.
Several researchers have proposed control methods such as "feedforward+feedback" and "feedforward+model+feedback", but these methods still have the following problems in actual operation:
(1) The feedback control system maintains higher DO concentration, generally above 1.5mg/L, and the anaerobic phosphorus release of the sludge is easy to occur in the secondary sedimentation tank, so that the phosphorus removal effect is poor, and the effluent P is influenced to reach the standard; the higher DO concentration, while preventing anaerobic phosphorus release from the secondary sedimentation tank, is not energy efficient.
(2) In actual operation, the DO concentration of the aerobic tank is difficult to control effectively for the following reasons:
(1) the on-line monitoring data of the inflow water is discontinuous, and a group of data is usually only available for about 2 hours, and the water quality data has certain fluctuation in the interval time (for a sewage treatment plant in a built-up area, the inflow water quality is relatively stable, and the fluctuation value is generally smaller);
(2) certain fluctuation exists in the water inflow B/C, a certain allowance is not always considered on the basis of theoretical estimation in the control of the aeration air quantity, and when the fluctuation of water quality is obvious, the calculated theoretical air supply quantity may not be enough, so that the water outflow index does not reach the standard.
(3) Because the sewage needs a certain time from an online monitoring point to the aerobic tank, the online monitoring instrument also needs a certain working time from sampling to output of results, and the lag time difference is not considered by the accurate aeration control system, the air supply quantity calculated by the water inlet actual measurement water quality data does not correspond to the air supply quantity required by the actual water quality at the aeration position of the aerobic tank, so that the effect of accurate aeration cannot be achieved.
(4) The existing control method for simulating the biological reaction process by using the activated sludge ASM model technology and further controlling the accurate air distribution of the fan is still immature, and because the ASM model mechanism is still in development, and model parameters are more, besides basic data such as the design water quantity and the water quality, parameters such as reaction dynamics of a biological tank, a sedimentation tank, a water pump, the fan and the like are also included, the actual requirement is high, the control process is complex, the investment and maintenance engineering quantity of each monitoring instrument is large, and the quality requirement on maintenance personnel is high, so that the actual effect is not ideal, and certain limitation exists and the method is to be further improved.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the invention provides a predictive accurate aeration method of feedforward and feedback assistance to control the oxygen supply of a biological treatment system, so that the control is easier and the operation is more energy-saving.
In the existing design, the tank capacity of the aerobic and anoxic tanks is designed according to the water quality of the inlet water and the outlet water and the most unfavorable temperature (10 ℃) so that the water quality of the outlet water is obviously superior to the designed water quality in practice, and a new balance is achieved.
The oxygen demand of the aerobic tank is designed according to the water quality of the designed inlet water and the designed outlet water, the theoretical oxygen demand is calculated, then the theoretical oxygen demand is converted into the oxygen demand in a standard state, and the oxygen demand is further converted into the standard air supply quantity, so that the operation of the fan is controlled. The higher the DO concentration of the reaction tank is, the larger the oxygen demand in the standard state is; in addition, oxygen delivery has an efficiency problem related to water depth, aerator efficiency, DO concentration, etc., whether it is adjustable or DO, if the physical conditions are determined. Thus, ensuring that the reaction tank DO is at a low level is a good solution for energy-efficient operation.
Therefore, the invention provides a control logic of a predictive accurate aeration method of feedforward and feedback assistance, which is used for controlling the oxygen supply of a biological treatment system and comprises the following steps:
step one, actually measuring COD of inlet water of a sewage treatment plant for a plurality of days Cr And BOD 5 Statistical analysis is performed to monitor the COD of the inlet water newly Cr Taking the historical COD as a benchmark Cr Historical COD within a certain set proportion range (such as 20%) of the data Cr And corresponding BOD 5 The value is used as the data set of probability distribution, B/C value in a certain set cumulative probability range (such as 80%) of B/C in the data set and average value of B/C in the data set are calculated, and the average value is used as BOD 5 The conversion coefficient, the safety coefficient K of the actual air supply quantity is calculated according to the following formula Anan (safety) ：
In the formula, B/C is BOD 5 /COD Cr Is a ratio of (2);
step two, utilizing an on-line monitoring instrument of a sewage treatment plant at intervals t Worker's work The obtained actual measurement of inflow COD Cr Ammonia nitrogen in the feed water, TN value in the feed water and BOD 5 Conversion coefficient and BOD design 5 Calculating the actual oxygen demand AOR of the aerobic zone by the total Kjeldahl nitrogen and nitrate nitrogen value; t is t Worker's work The working time from sampling to outputting results for the on-line monitoring instrument;
converting the actual oxygen demand AOR into oxygen demand SOR under standard state (0.1 MPa, 20 ℃) and calculating the standard air supply G s ；
Step four, actual air supply amount G s-control Based on theoretical deduction, multiplying by a safety factor K greater than 1 Anan (safety) Is calculated by the following method:
G s-control ＝G s ×K Anan (safety) ；
Step five, the control system at t Stagnation of food The air supply amount G s-control Control cabinet transmitted to fan unit and according to actual air supply G s-control Adjusting the output air quantity of the fan;
t stagnation of food For the time required by the sewage from an online monitoring point to an aerobic tank, t Stagnation of food The calculation mode of (a) is as follows: t is t Stagnation of food ＝t Stop and stop －t Worker's work Wherein t is Stop and stop The actual residence time of the sewage from the online monitoring point to the aerobic tank is shown;
step six, the feedback auxiliary control system feeds back the DO value of the end of the aerobic tank in real time, and sets the minimum DO value of DO min To prevent the secondary sedimentation tank from generating anaerobic phosphorus release, if DO value is larger than DO min The system is not regulated, runs for a period of time continuously, calculates new air quantity supply requirements after a new on-line monitoring value of the inflow water comes out, and then calculates G according to the calculated G s-control Adjusting; if DO value is less than DO min Then according to (DO min -current DO value) multiplied by the volume of the aerobic zone to obtain the oxygen demand AOR of the aerobic zone, and SOR, G are calculated again s 、K Anan (safety) Air volume G to be increased s increase In G s increase As an increased air supply of the fan set, oneDirectly increasing the air supply amount until the DO concentration of the aerobic tank exceeds DO min Stopping at a certain ratio (such as 10%) to ensure the lowest DO content of the effluent of the aerobic tank.
Preferably, in the second step, the actual oxygen demand AOR of the aerobic zone is calculated according to the following formula:
AOR＝0.001aQ(S o －S e )－cΔX V +b[0.001Q(N k －N ke )－0.12ΔX V ]
－0.62b[0.001Q(N t －N ke －N oe )－0.12ΔX V ]units: kgO 2 /d；
Wherein: s is S o BOD of the feed water to the biological reaction tank 5 Concentration (mg/L); s is S e Design BOD for biological reaction tank 5 Concentration (mg/L); n (N) t The actual measurement of the total nitrogen concentration (mg/L) of the inlet water of the biological reaction tank; n (N) k The actual measurement of the total Kjeldahl nitrogen concentration (mg/L) of the inlet water of the reaction tank is adopted; n (N) ke Designing the total Kjeldahl nitrogen concentration (mg/L) of water for the reaction tank; n (N) oe The concentration (mg/L) of nitrate nitrogen in water is designed for the reaction tank; a is the oxygen equivalent of carbon when the carbonaceous material is BOD 5 Timing, and taking 1.47; b is a constant, and the oxygen demand (kg O) required for oxidizing ammonia nitrogen per kg 2 /kgN), 4.57; c is a constant, and the oxygen equivalent of the bacterial cells is 1.42; q is the inflow water flow (m 3/d) of the biological reaction tank; ΔX V For discharging the microbiological mass (kg/d) of the bio-reaction cell system; 0.12 DeltaX V To remove nitrogen content (kg/d) from microorganisms in the biological reaction tank system.
Preferably, the biological reaction tank is used for feeding BOD 5 Concentration S o In order to take the average value of the B/C data set of the water inflow in the first step of statistics as a conversion coefficient, the COD of the water inflow is obtained by actual measurement Cr The value x reduction coefficient.
Specifically, BOD in the second step 5 The conversion factor is the average of the incoming water B/C dataset in step one.
Preferably, in the third step, the actual oxygen demand AOR is converted into the standard oxygen demand SOR according to the following formula:
wherein: c (C) S(20) The saturation degree of dissolved oxygen in clear water at the water temperature of 20 ℃ is mg/L; c (C) sb(T) For designing the saturation of average dissolved oxygen in the aerobic tank at the water temperature of T ℃, mg/L; t is the designed water temperature, DEG C; c (C) L The concentration of dissolved oxygen in the aerobic tank is mg/L; a is the ratio of the sewage oxygen transmission rate to the clear water oxygen transmission rate, and 0.82 is taken; ρ is a pressure correction factor, 1.0; beta is the ratio of saturated dissolved oxygen in sewage to saturated dissolved oxygen in clear water, and 0.95 is taken.
Preferably, the average dissolved oxygen saturation C in the aerobic tank sb The method is calculated according to the following formula:
wherein: c (C) s mg/L for oxygen saturation at atmospheric pressure; p is p b The absolute pressure at the outlet of the air diffusion device is Pa; q (Q) t Is the percentage of oxygen in the air bubbles when leaving the water surface of the aeration biological reaction tank.
Preferably, absolute pressure p b Calculated as follows:
P b ＝P+9.8×10 3 H
wherein: h is the installation depth of air diffusion, m; p is atmospheric pressure, 1.013X10 is taken 5 Pa。
Preferably, the percentage of oxygen Q t Calculated as follows:
wherein: e (E) A Oxygen transfer efficiency,%, for an air diffusion device.
Preferably, in step three, the standard gas supply amount G s Calculated as follows:
wherein: e (E) A Oxygen transfer efficiency,%, for an air diffusion device.
Compared with the prior art, the invention has the beneficial effects that:
1. the aeration control of the invention takes feedforward as the main material and DO feedback as the auxiliary material, which not only can ensure the water quality of the effluent, but also can realize energy conservation and consumption reduction, and is more reasonable in theory, feasible in practical operation, more energy-saving in operation and lower in carbon emission of the system;
2. the control of the air quantity is based on theoretical deduction, multiplied by a safety coefficient K which is larger than 1 Anan (safety) The control system can be adjusted at any time according to actual running conditions, so that insufficient air supply quantity caused by water quality fluctuation is avoided; the value of the safety coefficient is based on the probability distribution characteristic of B/C of the inlet water of the sewage treatment plant, so as to monitor the COD of the inlet water newly Cr Taking historical COD within a certain set proportion range (such as 20%) above and below the standard Cr And corresponding BOD 5 The value is used as a calculated data set, the B/C value with the cumulative probability of 80% in the data set is initially taken and divided by the average value of the B/C value to obtain the initial value of the safety coefficient K ampere, and the data set is further sequentially tested to obtain the latest monitored COD Cr 10-30% up and down, or taking B/C value with accumulation probability of 90-70% to calculate K Anan (safety) Determining proper K according to whether the effluent quality meets the standard Anan (safety) Selecting the optimal calculation K when the effluent quality reaches the standard Anan (safety) Value, obtain the controlled air quantity G s-control ；
3. The system scientifically sets the delay time t of DO supply and demand of the aerobic tank Stagnation of food According to the actual residence time t of sewage from an online monitoring point to an aerobic tank Stop and stop Subtracting the working time t from sampling to outputting result of the on-line monitoring instrument Worker's work Considering, the accuracy of aeration quantity prediction can be effectively improved;
4. the feedback mechanism of the DO at the tail end of the aerobic tank is reserved, and the operation parameters can be adjusted at any time in the system according to the operation condition, so that the adaptability of the system is greatly improved; the DO feedback is utilized to carry out auxiliary control on the aeration quantity, so that the lowest DO content of the effluent of the aerobic tank is ensured, the energy consumption is reduced, and meanwhile, the anaerobic phosphorus release of the secondary sedimentation tank is prevented;
5. the system can be controlled by adopting the conventional online monitoring index, any additional monitoring instrument is not needed to be added, and for the reconstruction project, only the control program is needed to be adjusted, so that the system deployment is simple and convenient.
Drawings
For a clearer description of the technical solutions of the embodiments of the present invention, the drawings that are needed in the description of the embodiments will be briefly introduced below, it being obvious that the drawings in the description below are only some embodiments of the present invention, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art, wherein:
FIG. 1 is a schematic diagram of a control system for a conventional biochemical pond feedback aeration system;
FIG. 2 is a schematic diagram of predictive precision aeration control for "feedforward+feedback assist" of a biochemical tank provided by the present invention.
Detailed Description
It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.
Example 1
As shown in FIG. 2, the living being isThe oxygen supply control logic of the processing system is changed into a mode of feedforward and feedback assistance, and the real-time changing water quality of the inlet water is obtained every 2 hours or so through an on-line detection instrument, including the BOD of the inlet water 5 Ammonia nitrogen in the feed water, TN value in the feed water and BOD 5 Conversion coefficient and design of water quality index value (BOD) 5 Total kjeldahl nitrogen, nitrate nitrogen value), etc., because of the BOD of the feed water 5 The data need to be measured for more than five days, and the COD of the inflow water Cr The data can be rapidly determined, thus by counting BOD of the incoming water 5 /COD Cr The average value of (i.e., B/C ratio) is used as a conversion coefficient by taking the COD of the incoming water Cr Multiplying the data by the conversion coefficient to obtain BOD of the incoming water 5 Thereby shortening the BOD of the inlet water 5 The monitoring time of the aeration can be adjusted more timely.
The oxygen demand of the aerobic tank is based on the BOD removed 5 The amount, the nitrogen amount and the like are calculated and determined, and the actual oxygen supply amount should consider the influence of factors such as the fluctuation of the water inlet amount and the water inlet quality, the temperature of the mixed liquid of the reaction tank and the like. According to the outdoor drainage design standard GB 50014-2021, the actual oxygen demand AOR of the aerobic zone in the biological reaction tank can be calculated as follows:
AOR＝0.001aQ(S o －S e )－cΔX V +b[0.001Q(N k －N ke )－0.12ΔX V ]－0.62b[0.001Q(N t －N ke －N oe )－0.12ΔX V ]units: kgO 2 /d；
Wherein: s is S o BOD of the feed water to the biological reaction tank 5 Concentration (mg/L) is calculated by taking the average value of the B/C data set of the water inflow in the first step as a conversion coefficient by actually measuring COD of the water inflow Cr Obtaining a value multiplied by a conversion coefficient; s is S e Design BOD for biological reaction tank 5 Concentration (mg/L); n (N) t The actual measurement of the total nitrogen concentration (mg/L) of the inlet water of the biological reaction tank; n (N) k The actual measurement of the total Kjeldahl nitrogen concentration (mg/L) of the inlet water of the reaction tank is adopted; n (N) ke Designing the total Kjeldahl nitrogen concentration (mg/L) of water for the reaction tank; n (N) oe The concentration (mg/L) of nitrate nitrogen in water is designed for the reaction tank; a is the oxygen equivalent of carbon when the carbonaceous material is BOD 5 Timing, and taking 1.47; b is a constant, oxidize per kilogramOxygen demand (kg O) for ammonia nitrogen 2 /kgN), 4.57; c is a constant, and the oxygen equivalent of the bacterial cells is 1.42; q is the inflow water flow (m 3/d) of the biological reaction tank; ΔX V For discharging the microbiological mass (kg/d) of the bio-reaction cell system; 0.12 DeltaX V To remove nitrogen content (kg/d) from microorganisms in the biological reaction tank system.
The actual oxygen demand AOR was converted into oxygen demand SOR in a standard state (0.1 MPa, 20 ℃ C.), and the conversion was performed according to the following formula:
wherein: c (C) S(20) The saturation degree of dissolved oxygen in clear water at the water temperature of 20 ℃ is mg/L; c (C) sb(T) For designing the saturation of average dissolved oxygen in the aerobic tank at the water temperature of T ℃, mg/L; t is the designed water temperature, DEG C; c (C) L The concentration of dissolved oxygen in the aerobic tank is mg/L; a is the ratio of the sewage oxygen transmission rate to the clear water oxygen transmission rate, and 0.82 is taken; ρ is a pressure correction factor, 1.0; beta is the ratio of saturated dissolved oxygen in sewage to saturated dissolved oxygen in clear water, and 0.95 is taken.
Average dissolved oxygen saturation C in aerobic tank sb The method is calculated according to the following formula:
wherein: c (C) s mg/L for oxygen saturation at atmospheric pressure; p is p b The absolute pressure at the outlet of the air diffusion device is Pa; q (Q) t Is the percentage of oxygen in the air bubbles when leaving the water surface of the aeration biological reaction tank.
Absolute pressure p b Calculated as follows:
P b ＝P+9.8×10 3 H
wherein: h is the installation depth of air diffusion, m; p is atmospheric pressure, 1.013X10 is taken 5 Pa。
Percentage of oxygen Q t Calculated as follows:
wherein: e (E) A Oxygen transfer efficiency,%, for an air diffusion device.
Air supply amount G in standard state s (m 3 And/h) is calculated as follows:
wherein: e (E) A Oxygen transfer efficiency,%, for an air diffusion device.
The control of the air quantity is considered to multiply a safety coefficient K which is larger than 1 on the basis of theoretical deduction Anan (safety) And the control system can be adjusted at any time according to actual running conditions, so that insufficient air supply quantity caused by water quality fluctuation is avoided. Safety factor K of the present embodiment Anan (safety) The method is as follows:
for sewage treatment plant to actually measure COD of inflow water for multiple days Cr And BOD 5 Statistical analysis is performed to monitor the COD of the inlet water newly Cr Taking the historical COD as a benchmark Cr COD within a certain set proportion range (such as 20%) of the data Cr And corresponding BOD 5 The value is used as a calculated data set, the B/C value in a certain set cumulative probability range (such as 80%) of the B/C in the data set and the average value of the B/C in the data set are calculated, the average value is used as a conversion coefficient, and the safety coefficient K of the actual air supply quantity is calculated according to the following formula Anan (safety) ：
In the formula, B/C is BOD 5 /COD Cr Is a ratio of (2).
Safety factor K of the present embodiment Anan (safety) The value of (2) is based on the probability distribution characteristic of B/C of inlet water of sewage treatment plant, and the latest monitored COD is used first Cr Taking the historical COD as a benchmark Cr DataHistorical COD of the upper and lower 20% probability distribution in (3) Cr And corresponding BOD 5 The value is taken as a data set of probability distribution, and the B/C value with the cumulative probability of 80% in the data set (namely, the probability that a certain B/C value occurs in a cumulative way accounts for 80%) is divided by the average value of the B/C values to obtain the value. In specific implementation, the method comprises the following steps: according to the latest monitored COD of a sewage treatment plant Cr 180mg/L COD was obtained with 20% probability distribution Cr In the range of 144-216 mg/L, corresponding BOD 5 The value is used as a data set of probability distribution, the B/C value with 80% of cumulative probability in the data set is calculated to be 0.54, the average value of the B/C values is calculated to be 0.47, and then the conversion coefficient is calculated to be 0.47, K Anan (safety) =0.54/0.47=1.14. The latest monitored COD can be further obtained by sequentially testing the data set according to whether the water quality of the effluent reaches the standard or not Cr 10-30% up and down, or taking B/C value with accumulation probability of 90-70% to calculate K Anan (safety) 。
Therefore, the best K is selected according to whether the water quality of the effluent meets the standard Anan (safety) Value to obtain controlled air volume G s-control Actual air supply amount G s-control Calculated as follows:
G s-control ＝G s ×K Anan (safety) 。
The system considers the time hysteresis, and the sewage from the on-line monitoring point to the aerobic tank needs a certain time t Stagnation of food The initial value is t according to the actual residence time of the sewage from an online monitoring point to an aerobic tank Stop and stop Subtracting the working time t from sampling to outputting result of the on-line monitoring instrument Worker's work Consider the following formula:
t stagnation of food ＝t Stop and stop －t Worker's work
The system should consider the above parameter t Stop and stop And t Worker's work Is adjustable and can be flexibly adjusted according to actual running conditions. In A way 2 O is taken as an example, according to the outdoor drainage design standard GB 50014-2021, the retention time of an aeration grit chamber is 15min, the retention time of an anaerobic zone is 1.5h, the retention time of an anoxic zone is 6h, then tTing=0.25+1.5+6=7.75 h, the retention time of sewage in a pipeline is ignored, and the measurement time of inflow COD is 30 min (rapid digestion spectrophotometry, rapid digestion method) to 2h (heavy chromium)Acid salt reflux method, spectrophotometry), taking the time t from sampling to outputting the result of an on-line monitoring instrument Worker's work =3h, then t Stagnation of food ＝t Stop and stop －t Worker's work ＝7.75-3＝4.75h。
Thus, the control system is at t Stagnation of food The air supply amount G s-control Control cabinet transmitted to fan unit and according to actual air supply G s-control And adjusting the output air quantity of the fan.
The DO meter at the tail end of the aerobic tank is used as a feedback auxiliary control, and the function of the DO meter is not to monitor whether the DO value is about 2.0mg/L, but to prevent the condition that the anaerobic phosphorus release occurs in the secondary sedimentation tank, so that the effluent P is affected to reach the standard. When the system is designed specifically, DO feedback enables the DO concentration initial value at the tail end of the aerobic tank to be about 0.4-0.5 mg/L, the DO value in the system is adjustable as an auxiliary control condition, and when the system is actually operated, due to different conditions of each sewage treatment plant, such as different surface loads, different diameter-depth ratios, different mud bucket sizes and the like of the secondary sedimentation tank, the DO at the tail end of the aerobic tank needs to be debugged and monitored, and the proper DO concentration is found so as to meet the condition that anaerobic phosphorus release of the secondary sedimentation tank does not occur.
The feedback auxiliary control system feeds back the DO value of the tail end of the aerobic tank in real time, and sets the minimum DO value of DO min To prevent the secondary sedimentation tank from generating anaerobic phosphorus release, if DO value is larger than DO min The system is not regulated, continuously runs for 2 hours until a new online monitoring value of the inflow water comes out, calculates a new air quantity supply requirement, and then calculates G according to the calculated G s-control Adjusting; if DO value is less than DO min Then according to (DO min -current DO value) multiplied by the volume of the aerobic zone to obtain the oxygen demand AOR of the aerobic zone, and SOR, G are calculated again s 、K Anan (safety) Air volume G to be increased s increase In G s increase As the air supply amount of the increased fan set, the air supply amount is increased until the DO concentration of the aerobic tank exceeds DO min Stopping at a certain ratio (such as 10%) to ensure the lowest DO content of the effluent of the aerobic tank.
The foregoing description is only illustrative of the present invention and is not intended to limit the scope of the invention, and all equivalent structures or equivalent processes or direct or indirect application in other related arts are included in the scope of the present invention.
Claims (4)
1. A predictive accurate aeration method is characterized in that: the method comprises the following steps:
step one, actually measuring COD of inlet water of a sewage treatment plant for a plurality of days Cr And BOD 5 Statistical analysis is performed to monitor the COD of the inlet water newly Cr Taking the historical COD as a benchmark Cr Historical COD within a certain set proportion range of up and down in data Cr And corresponding BOD 5 The value is used as a data set of probability distribution, the B/C value in a certain set cumulative probability range of the B/C in the data set and the average value of the B/C in the data set are calculated, the average value is used as a conversion coefficient, and the safety coefficient K of the actual air supply quantity is calculated according to the following formula Anan (safety) ：
In the formula, B/C is BOD 5 /COD Cr Is a ratio of (2);
step two, utilizing an on-line monitoring instrument of a sewage treatment plant at intervals t Worker's work The obtained actual measurement of inflow COD Cr Ammonia nitrogen in the feed water, TN value in the feed water and BOD 5 Conversion coefficient and BOD design 5 Calculating the actual oxygen demand AOR of the aerobic zone by the total Kjeldahl nitrogen and nitrate nitrogen value;
t worker's work The working time from sampling to outputting results for the on-line monitoring instrument;
step three, converting the actual oxygen demand AOR into oxygen demand SOR in a standard state, and calculating a standard air supply G s ；
Step four, actual air supply amount G s-control Based on theoretical deduction, multiplying by a safety factor K greater than 1 Anan (safety) Is calculated by the following method:
G s-control ＝G s ×K Anan (safety) ；
Step five, the control system at t Stagnation of food Will thenAir supply amount G s-control Control cabinet transmitted to fan unit and according to actual air supply G s-control Adjusting the output air quantity of the fan;
t stagnation of food For the time required by the sewage from an online monitoring point to an aerobic tank, t Stagnation of food The calculation mode of (a) is as follows: t is t Stagnation of food ＝t Stop and stop －t Worker's work Wherein t is Stop and stop The actual residence time of the sewage from the online monitoring point to the aerobic tank is shown;
step six, the feedback auxiliary control system feeds back the DO value of the end of the aerobic tank in real time, and sets the minimum DO value of DO min To prevent the secondary sedimentation tank from generating anaerobic phosphorus release, if DO value is larger than DO min The system is not regulated, runs for a period of time continuously, calculates new air quantity supply requirements after a new on-line monitoring value of the inflow water comes out, and then calculates G according to the calculated G s-control Adjusting; if DO value is less than DO min Then according to (DO min -current DO value) multiplied by the volume of the aerobic zone to obtain the oxygen demand AOR of the aerobic zone, and SOR, G are calculated again s 、K Anan (safety) Air volume G to be increased s increase In G s increase As the air supply amount of the increased fan set, the air supply amount is increased until the DO concentration of the aerobic tank exceeds DO min Is stopped at a certain ratio of the number of times.
2. A predictive precision aeration method as claimed in claim 1, wherein: in the second step, the actual oxygen demand AOR of the aerobic zone is calculated according to the following formula:
AOR＝0.001aQ(S o －S e )－cΔX V +b[0.001Q(N k －N ke )－0.12ΔX V ]－0.62b[0.001Q(N t －N ke －N oe )－0.12ΔX V ]units: kgO 2 /d；
Wherein: s is S o BOD of the feed water to the biological reaction tank 5 Concentration (mg/L); s is S e Design BOD for biological reaction tank 5 Concentration (mg/L); n (N) t The actual measurement of the total nitrogen concentration (mg/L) of the inlet water of the biological reaction tank; n (N) k The actual measurement of the total Kjeldahl nitrogen concentration (mg/L) of the inlet water of the reaction tank is adopted; n (N) ke Designing the total Kjeldahl nitrogen concentration (mg/L) of water for the reaction tank; n (N) oe The concentration (mg/L) of nitrate nitrogen in water is designed for the reaction tank; a is the oxygen equivalent of carbon when the carbonaceous material is BOD 5 Timing, and taking 1.47; b is a constant, and the oxygen demand (kg O) required for oxidizing ammonia nitrogen per kg 2 /kgN), 4.57; c is a constant, and the oxygen equivalent of the bacterial cells is 1.42; q is the inflow water flow (m 3/d) of the biological reaction tank; ΔX V For discharging the microbiological mass (kg/d) of the bio-reaction cell system; 0.12 DeltaX V To remove nitrogen content (kg/d) from microorganisms in the biological reaction tank system.
3. A predictive precision aeration method as claimed in claim 2, wherein: BOD of the feed water of the biological reaction tank 5 Concentration S o In order to take the average value of the B/C data set of the water inflow in the first step of statistics as a conversion coefficient, the COD of the water inflow is obtained by actual measurement Cr The value x reduction coefficient.
4. A predictive precision aeration method as claimed in claim 1, wherein: BOD in the second step 5 The conversion factor is the average of the incoming water B/C dataset in step one.
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