A sewage treatment plant biological tank anoxic section denitrification control method and device

Abstract

The present application provides a kind of sewage treatment plant biological pond anoxic section denitrification control method and device, method includes the following steps: using carbon source experimental system carries out carbon source denitrification experiment and carbon source COD degradation experiment, and calculates the denitrification rate of sludge, carbon source denitrification denitrification ratio and COD degradation rate;Anoxic section influent flow, anoxic section volume, aerobic section volume, anoxic section sludge concentration, sludge concentration tank sludge concentration, aerobic section sludge concentration, anoxic section influent nitrate nitrogen concentration are collected;Calculate the amount of anoxic section nitrate nitrogen removal and the amount of anoxic section nitrate nitrogen removal required;Adjust carbon source dosage and activated sludge dosage.The present application determines carbon source dosage and sludge dosage through the actual denitrification denitrification rate, denitrification ratio and other data of sewage treatment plant biological pond anoxic section, improves the denitrification effect of anoxic section, meets the total nitrogen discharge requirement of sewage treatment plant water quality.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and in particular relates to a method and device for controlling denitrification in the anoxic section of a biological tank in a wastewater treatment plant. Background Technology

[0002] In the anoxic zone of the biological treatment plant's biological treatment tank, denitrifying bacteria utilize organic matter to carry out denitrification under anoxic conditions, removing nitrate nitrogen from the wastewater and achieving denitrification. The denitrification efficiency in the anoxic zone is affected by factors such as sludge activity, sludge quantity, and carbon source dosage. Currently, urban wastewater treatment plants generally suffer from low influent C / N ratios, resulting in insufficient carbon source for denitrification in the biological treatment tank and limiting denitrification efficiency. Simultaneously, wastewater treatment plant effluent TN (total nitrogen) discharge requirements are becoming increasingly stringent, with many local standards requiring TN ≤ 10 mg / L. To meet these effluent TN requirements, external carbon sources need to be added to improve denitrification efficiency.

[0003] Existing technologies mainly focus on carbon source screening methods and intelligent dosing control methods. The amount of carbon source added is often calculated based on empirical denitrification ratios (C / N = 4-6:1) or theoretical denitrification ratios (C / N = 2.86:1). These values ​​often differ significantly from actual values, and the denitrification ratios vary considerably between different types of carbon sources and activated sludge carbon sources with different properties. For example, patent CN 114538612A describes an external carbon source precision dosing system and its control method, which precisely controls carbon source addition based on the influent nitrification load and effluent nitrification concentration in the anoxic section, using a combination of feedforward and feedback methods.

[0004] In actual operation of wastewater treatment plants, the denitrification efficiency of different carbon sources and the carbon source utilization rate of activated sludge vary. If the amount of activated sludge, organic matter, and microbial adaptability to organic matter in the anoxic zone are not considered, simply increasing the amount of carbon source added will not completely degrade the added carbon source within the retention time when the amount of activated sludge in the biological tank is insufficient. This will not only fail to effectively reduce total nitrogen but will also cause COD in the effluent to exceed the standard, and the actual effect will not achieve the expected goal. Summary of the Invention

[0005] Nitrogen removal in wastewater treatment plants involves denitrifying bacteria reducing nitrates to nitrogen gas in anoxic conditions within the anoxic zone, thus achieving nitrogen removal. The denitrification capacity of the anoxic zone is directly related to the carbon source denitrification rate, activated sludge concentration, and retention time. The denitrification rate is primarily related to the type of carbon source, substrate concentration, and the adaptability of the activated sludge microorganisms. To control denitrification in the anoxic zone of wastewater treatment plants, ensuring the nitrate nitrogen level in the effluent meets requirements while preventing COD exceedances, this invention aims to overcome the shortcomings of existing technologies by proposing a method and device for controlling denitrification in the anoxic zone of a wastewater treatment plant's biological treatment tank. This invention can effectively control the denitrification effect in the anoxic zone of a wastewater treatment plant's biological treatment tank, adjust the carbon source and activated sludge dosage in the anoxic zone, improve the denitrification effect, and meet the wastewater treatment plant's discharge standards.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] In a first aspect, the present invention provides a method for controlling denitrification in the anoxic section of a biological treatment plant, comprising the following steps:

[0008] Step S1: Conduct carbon source denitrification and carbon source COD degradation experiments using a carbon source experimental system, and calculate the denitrification rate K of the sludge. N Carbon source denitrification nitrogen removal ratio M W0 and COD degradation rate Kc;

[0009] Step S2: Collect the influent flow rate Q of the anoxic section, the volume V1 of the anoxic section, the volume V2 of the aerobic section, and the sludge concentration M of the anoxic section. L1 , Sludge concentration M in sludge thickening tank L2 aerobic sludge concentration M L3 1. Nitrate nitrogen concentration C in the influent of the anoxic section N1 ;

[0010] Step S3: Calculate the removal amount N of nitrate nitrogen in the anoxic zone based on the calculation results of Step S1 and the parameters collected in Step S2. W计 The amount of nitrate nitrogen (N) that needs to be removed in the anoxic section W需 ;

[0011] Step S4: Calculate N based on step S3. W计 and N W需 Adjust the amount of carbon source and activated sludge added.

[0012] In some embodiments, the denitrification rate K in step S1 N The calculation formula is:

[0013] K N =(C N1 -C N2 ) / MLN / H

[0014] Among them, K N C represents the denitrification rate of carbon source, expressed in mgNO3-N / (mgMLSS·h); N1 The concentration of nitrate nitrogen before the experiment is expressed in mg / L; C N2 M represents the nitrate nitrogen concentration after the experiment, in mg / L. LN The concentration of activated sludge in the carbon source denitrification experiment is in mg / L; H is the reaction time in hours.

[0015] In some embodiments, the carbon source denitrification ratio M in step S1 W0 The calculation formula is:

[0016] M W0 =(C C1 -C C2 ) / (C N1 -C N2 )

[0017] Among them, M W0 The carbon source denitrification nitrogen removal ratio is the amount of COD consumed to remove a unit of nitrate nitrogen, expressed in mgCOD / mgTN; C C1 The initial COD concentration after adding the carbon source is expressed in mg / L; C C2 COD concentration after the experiment, in mg / L; C N1 The concentration of nitrate nitrogen before the experiment is expressed in mg / L; C N2 This represents the concentration of nitrate nitrogen after the experiment, in mg / L.

[0018] In some embodiments, the formula for calculating the COD degradation rate Kc in step S1 is:

[0019] Kc=(C C3 -C C4 ) / M LC / H

[0020] Among them, K C The carbon source represents the aerobic COD degradation rate, expressed in mgCOD / (mgMLSS·h), C C3 The COD concentration before the carbon source COD degradation experiment is expressed in mg / L; C C4 M represents the COD concentration after the carbon source COD degradation experiment, in mg / L. LC The concentration of activated sludge in the COD degradation experiment is mg / L; H is the reaction time in hours.

[0021] In some embodiments, N in step S3 W计The calculation formula is as follows:

[0022] N W计 =K N *M L1 *V1

[0023] Where, N W计 Calculate the removal rate of nitrate nitrogen in the anoxic zone, in g / h; K N V1 is the denitrification rate, expressed in mgNO3-N / (mgMLSS·h); V1 is the volume of the anoxic zone, expressed in m³. 3 M L1 The concentration of sludge in the anoxic zone is expressed in mg / L.

[0024] In some embodiments, N in step S3 W需 The calculation formula is as follows:

[0025] N W需 =Q*(C N1 -C N0 )

[0026] Where, N W需 The amount of nitrate nitrogen to be removed in the anoxic zone, expressed in g / h; C N0 The expected nitrate nitrogen value at the outlet of the anoxic section, in mg / L; C N1 Q represents the nitrate nitrogen concentration in the influent to the anoxic section, in mg / L; Q represents the influent flow rate to the anoxic section, in m³ / s. 3 / h;

[0027] In some embodiments, the adjustment operation in step S4 is as follows:

[0028] When N W计 ≥N W需 When the amount of activated sludge in the anoxic zone is sufficient, there is no need to add more activated sludge; at this time, only a carbon source needs to be added.

[0029] When N W计 <N W需 If the amount of activated sludge in the anoxic zone is insufficient, more activated sludge needs to be added.

[0030] In some embodiments, the formula for calculating the amount of carbon source added is:

[0031] Q 碳 =1000*M W0 *(C N1 -C N0 )*Q / N C +1000*γ*K C *M L3 *V2

[0032] Among them, Q 碳The amount of carbon source added is expressed in L / h; N C γ is the carbon source COD equivalent, in g / L; γ is the safety factor, ranging from 0.1 to 0.5; M L3 V1 is the concentration of activated sludge at the front end of the aerobic tank, in mg / L; V2 is the volume of the aerobic section, in m³. 3 M L3 The concentration of sludge in the aerobic section is expressed in mg / L.

[0033] In some embodiments, the formula for calculating the dosage of activated sludge is as follows:

[0034] Q 泥 =(QM L1 -QM L目 ) / (M L目 -M L2 );

[0035] Among them, Q 泥 This refers to the amount of activated sludge added, in cubic meters (m³). 3 / h;M L目 Q represents the target sludge concentration in the anoxic zone, in mg / L; Q represents the influent flow rate in the anoxic zone, in m³ / s. 3 / h;M L2 Sludge concentration M in sludge thickening tank L2 The unit is mg / L; M L1 The concentration of sludge in the anoxic zone is expressed in mg / L.

[0036] Target sludge concentration M in the anoxic section L目 The calculation formula is:

[0037] M L目 =Q*(C N1 -C N0 ) / K N / V1

[0038] Where Q is the influent flow rate of the anoxic section, in m³ / s. 3 / h;C N1 The concentration of nitrate nitrogen in the influent of the anoxic section is expressed in mg / L; C N0 The expected nitrate nitrogen value at the outlet of the anoxic section, in mg / L; K N V1 is the denitrification rate, expressed in mgNO3-N / (mgMLSS·h); V1 is the volume of the anoxic zone, expressed in m³. 3 .

[0039] In some embodiments, when M L目 When the value exceeds the maximum value of the secondary sedimentation tank, M L最大(The wastewater treatment plant shall determine the appropriate level of concentration based on the actual operation of the secondary sedimentation tank.) The sludge concentration shall be adjusted according to the maximum value. If the nitrate nitrogen in the effluent of the anoxic zone still does not meet the expected value, the carbon source shall be replaced.

[0040] In some embodiments, the original carbon source is replaced with a new carbon source with a faster denitrification rate.

[0041] Secondly, the present invention also provides a denitrification control device for the anoxic section of a biological treatment plant, the device comprising:

[0042] The online monitoring system is used to monitor in real time the influent flow rate of the anoxic zone, the nitrate nitrogen concentration of the influent of the anoxic zone, the sludge concentration of the anoxic zone, the sludge concentration of the sludge thickener, the carbon source dosage, and the sludge dosage, and sends these parameters to the automatic control system.

[0043] The carbon source experimental system is used to detect the denitrification rate and denitrification nitrogen removal ratio of the carbon source, and send the denitrification rate and denitrification nitrogen removal ratio to the automatic control system.

[0044] The automatic control system is used to determine the carbon source reagent and sludge addition adjustment method based on the influent flow rate of the anoxic zone, the nitrate nitrogen concentration of the influent of the anoxic zone, the sludge concentration of the anoxic zone, the carbon source denitrification rate, and the denitrification ratio, and to send reagent addition control signals and activated sludge addition control signals.

[0045] In some embodiments, the carbon source experimental system includes a denitrification experimental container, a carbon source COD degradation experimental container, an electric stirrer, a filter, a vacuum sludge pump, an aeration disc, and a blower; the upper part of the experimental container is provided with a volume-fixing port for fixed-volume activated sludge; the bottom is provided with a drain port for emptying the container after the experiment; during the experiment, the vacuum sludge pump extracts activated sludge from the front and end of the anoxic section; this avoids stirring and dispersing the sludge mixture, which would damage the sludge flocs, and allows the experimental sludge to more accurately reflect the state of the activated sludge in the anoxic section.

[0046] In some embodiments, the automatic control system includes a control module and a display module. The control module is connected to an electric stirrer, a return sludge pump, a COD sampling pump, a vacuum sludge pump, a dosing pump, a blower, and the display module, respectively. The control module controls the operation of each component and performs data processing. The display module is connected to an online detection system. The display module enables the operator to input control information for the equipment and display the detection results. The display module includes an input device and a display.

[0047] In some embodiments, the online detection system includes an instantaneous flow meter, an online nitrate nitrogen meter, an online sludge concentration meter, an online COD meter, an online flow meter, and an online dissolved oxygen meter.

[0048] The instantaneous flow meter is used to measure the instantaneous flow rate of the influent in the anoxic section;

[0049] The online nitrate nitrogen meter is used to detect the nitrate nitrogen content in the influent of the anoxic section and the nitrate nitrogen content in the activated sludge solution of the denitrification experiment, respectively.

[0050] The online sludge concentration meter is used to detect the sludge concentration in the anoxic zone, the sludge concentration in the activated sludge solution of the denitrification experiment, the sludge concentration in the thickening tank, the sludge concentration in the mixed liquor of the carbon source COD degradation experiment, and the sludge concentration at the inlet of the aerobic tank.

[0051] The online COD detector is used to detect COD;

[0052] The online flow meters are used to detect the amount of carbon source added and the amount of activated sludge added, respectively.

[0053] The online dissolved oxygen meter is used to detect dissolved oxygen in the sludge mixture of the carbon source COD degradation experiment and to detect dissolved oxygen in the aerobic tank.

[0054] Compared with the prior art, the present invention has the following advantages:

[0055] This invention determines the denitrification capacity of the anoxic zone by conducting denitrification experiments on activated sludge in the anoxic zone. Based on the denitrification rate, the volume of the anoxic zone, and the sludge concentration, the theoretical nitrogen removal capacity of the anoxic zone is determined. Then, the actual amount of nitrate nitrogen to be removed in the anoxic zone is calculated by comparing the influent nitrate nitrogen concentration and the target concentration value. After comparing the theoretical nitrogen removal capacity and the actual amount of nitrate nitrogen to be removed in the anoxic zone, the sludge dosage and carbon source dosage are adjusted.

[0056] This invention solves the problem of excessive COD in wastewater treatment plants caused by blindly adding carbon sources. It determines the amount of carbon source or activated sludge to be added based on the actual denitrification capacity of the carbon source, ensuring that the amount of activated sludge and organic matter in the anoxic zone meets the denitrification conditions. It also makes the carbon source dosage more accurate, improves the denitrification effect in the anoxic zone, and meets the total nitrogen discharge requirements of wastewater treatment plants, thus having significant application value. Attached Figure Description

[0057] Figure 1 A schematic diagram of the denitrification control device in the anoxic section of a biological treatment plant.

[0058] Figure 2 This is a schematic diagram of the denitrification control method in the anoxic section of the biological treatment tank of a wastewater treatment plant.

[0059] Explanation of reference numerals in the attached figures:

[0060] 1-Online nitrate nitrogen meter; 2-Online sludge concentration meter; 3-Instantaneous flow meter; 4-Online nitrate nitrogen meter; 5, 6, 28, 29-Online sludge concentration meters; 7, 18-Online flow meters; 8-Dosing pump; 9, 23-Denitrification experimental container; 10, 24-Filter; 11-Online COD detector; 12, 27-Vacuum sludge pump; 13, 25-COD sampling pump; 14-Electric stirrer; 15-Return sludge pump; 16, 19-Volume control port; 17, 20-Drainage port; 21-Blower; 22-Aeration disc; 30-Online dissolved oxygen meter. Detailed Implementation

[0061] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0062] In this document, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0063] In this document, when values ​​are described as ranges, it should be understood that such disclosure includes disclosure of all possible subranges within that range, as well as the specific numerical values ​​falling within that range, regardless of whether the specific numerical value or specific subrange is explicitly specified.

[0064] In this article, the terms "multiple" or "more than" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0065] In this document, the terms "preferred" and "more preferred" are used only to describe implementation methods or embodiments with better effects, and should be understood as not constituting a limitation on the scope of protection of this invention.

[0066] In this document, terms such as "further" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0067] In this article, the term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0068] In this document, the term "about" means a specified value of + / - 10%, preferably + / - 5%, and more preferably + / - 1%.

[0069] In this article, the terms “include,” “including,” “have,” “contain,” etc., are all open-ended terms, meaning that they include but are not limited to.

[0070] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0071] This invention provides a denitrification control device for the anoxic section of a biological treatment plant, such as... Figure 1 As shown, the control device includes:

[0072] The device includes an online detection system, a carbon source experimental system, and an automatic control system.

[0073] The online monitoring system is used to monitor in real time the influent flow rate of the anoxic zone, the nitrate nitrogen concentration of the influent of the anoxic zone, the sludge concentration of the anoxic zone, the sludge concentration of the sludge thickener, the carbon source dosage, and the sludge dosage, and sends these parameters to the automatic control system.

[0074] The carbon source experimental system is mainly used to detect the denitrification rate and denitrification ratio of the carbon source, and send the denitrification rate and denitrification ratio to the automatic control system.

[0075] The automatic control system determines the carbon source reagent and sludge addition strategy based on the influent flow rate of the anoxic zone, the nitrate nitrogen concentration of the influent of the anoxic zone, the sludge concentration of the anoxic zone, the carbon source denitrification rate, and the denitrification ratio, and sends reagent addition control signals and activated sludge addition control signals.

[0076] Specifically, the online monitoring system includes an instantaneous flow meter 3 for measuring the instantaneous flow rate of the influent in the anoxic zone, an online nitrate nitrogen meter 1 for detecting the nitrate nitrogen content of the influent in the anoxic zone, an online sludge concentration meter 2 for detecting the sludge concentration in the anoxic zone, an online nitrate nitrogen meter 4 for detecting the nitrate nitrogen in the activated sludge solution of the denitrification experiment, an online sludge concentration meter 5 for detecting the sludge concentration in the activated sludge solution of the denitrification experiment, an online sludge concentration meter 6 for detecting the sludge concentration in the thickener, an online COD meter 11 for detecting COD, an online flow meter 18 for detecting the carbon source dosage, an online flow meter 7 for detecting the activated sludge dosage, an online dissolved oxygen meter 26 for detecting the dissolved oxygen in the sludge mixture of the carbon source COD degradation experiment, an online sludge concentration meter 29 for detecting the sludge concentration in the sludge mixture of the carbon source COD degradation experiment, an online sludge concentration meter 28 for detecting the sludge concentration at the inlet of the aerobic tank, and an online dissolved oxygen meter 30 for detecting the dissolved oxygen in the aerobic tank.

[0077] The carbon source experimental system consists of a denitrification experimental container 9, a carbon source COD degradation experimental container 23, an electric stirrer 14, a filter 10, vacuum sludge pumps 12 and 27, an aeration disc 22, and a blower 21. The upper parts of the experimental containers 9 and 23 are respectively equipped with volume-fixing ports 16 and 19 for fixed-volume determination of activated sludge, and the bottoms are respectively equipped with drain ports 17 and 20 for emptying the containers after the experiment. During the experiment, the vacuum sludge pumps 12 and 27 are used to extract activated sludge from the front and end of the anoxic section, respectively, to avoid stirring and dispersing the sludge mixture and destroying the sludge flocs, so that the experimental sludge more accurately reflects the state of the activated sludge in the anoxic section.

[0078] The automatic control system includes a control module and a display module. The control module is connected to the electric mixer 14, the return sludge pump 15, the COD sampling pumps 13 and 25, the vacuum sludge pumps 12 and 27, the chemical dosing pump 8, the blower 21, and the display module, respectively. The control module controls the operation of each component and processes data. The display module is connected to the online monitoring system, enabling the operator to input control information and display monitoring results. The display module includes an input device and a display screen.

[0079] The present invention will be described in detail below with reference to the embodiments. The methods in Embodiments 1 and 2 below both use the above-described apparatus.

[0080] Example 1

[0081] A wastewater treatment plant uses a three-stage AO process with a treatment capacity of 12,000 tons / day. The carbon source is added at the final anoxic stage, which has a volume of 1000 m³. 3 External reflux is 100%, sludge concentration is 4000 mg / L, and the final aerobic section volume is 1000 m³. 3 The design influent COD concentration is 400 mg / L, total nitrogen concentration is 50 mg / L, and ammonia nitrogen concentration is 40 mg / L. The effluent will comply with the Class A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002). The carbon source used in the plant is a composite carbon source with a COD equivalent of 200,000 mg / L.

[0082] The denitrification control method in the anoxic section of the biological treatment plant includes the following steps:

[0083] Step S1: Conduct a carbon source denitrification experiment using a carbon source experimental system. Take 50L of activated sludge from the anoxic zone and add it to the experimental container (total volume 70L). Record the initial nitrate nitrogen value (16.6mg / L) and sludge concentration of 4200mg / L. Add carbon source to carry out the denitrification experiment. The amount of composite carbon source added (C / N=5) is 20mL. Record the COD value after adding carbon source (115.4mg / L). Stop the experiment after reaching the set reaction time and record the COD value (75.3mg / L) and nitrate nitrogen value (11.6mg / L). The reaction time is the actual residence time of the anoxic zone.

[0084] Turn on the stirrer and start the sludge sampling pump (rated flow rate of 10L / min, effective volume of the experimental container of 70L). Open the injection solenoid valve to continuously feed activated sludge from the front end of the anoxic section (before the carbon source addition point) into the experimental container. After reaching the overflow level, close the injection solenoid valve. Read the value displayed on the online nitrate nitrogen meter at this time, control the stirring motor speed to maintain the mixing state in the experimental container. Add 20ml of composite carbon source, turn on the water sample sampling pump of the online COD detection equipment, and detect the initial COD value.

[0085] The actual residence time in the anoxic phase is H = V1 / Q = 1 hour, and the reaction time for the carbon source experiment is 1 hour.

[0086] Denitrification rate K N Calculation formula:

[0087] K N =(C N1 -C N2 ) / M LN / H=0.0012mgNO3-N / (mgMLSS·h);

[0088] Carbon source denitrification nitrogen removal ratio M W0 Calculation formula:

[0089] M W0 =(C C1 -C C2 ) / (C N1 -C N2 = 8 mg COD / mg TN;

[0090] A carbon source COD degradation experiment was conducted using a carbon source experimental system. 50L of activated sludge from the anoxic section outlet was added to the experimental container (total volume 70L). The initial COD value (28.7mg / L) and sludge concentration (4200mg / L) were recorded. The carbon source was then added to carry out the COD degradation experiment. The amount of carbon source added was 10mL, and the COD value after adding the carbon source was recorded (68.4mg / L). The experiment ended after 1 hour, and the COD value was recorded (30.4mg / L).

[0091] Turn on the agitator and start the sludge sampling pump (rated flow rate of 10L / min, effective volume of the bioreactor is 70L). Open the sampling solenoid valve to continuously feed activated sludge from the outlet of the anoxic section into the experimental container. After reaching the overflow level, close the sampling solenoid valve. Turn on the bottom aeration and read the dissolved oxygen in the experimental container. Control the blower to maintain the dissolved oxygen in the container at the same level as that in the aerobic section. Add 10ml of composite carbon source and turn on the online COD detection equipment's water sampling pump to detect the initial COD value.

[0092] Carbon source COD degradation rate Kc:

[0093] Kc=(C C1 -C C2 ) / M LC / H = 0.009 mg COD / (mg MLSS·h);

[0094] Step S2: Collect the influent flow rate Q value of the anoxic section at 1000 m³ / h 3 / h, hypoxic zone volume V1 value 1000m 3 aerobic section volume V2 value 1000m³ 3 , Sludge concentration M in the anoxic section L1 Value 4200mg / L, aerobic sludge concentration M L3 Value 4200mg / L, sludge concentration M in sludge thickening tank L2 Value 22000 mg / L, nitrate nitrogen concentration C in the influent of the anoxic section N1 Value 16 mg / L, denitrification rate K N The values ​​of NO3-N / (mgMLSS·h), COD degradation rate Kc value of carbon source 0.009mgCOD / (mgMLSS·h), denitrification ratio of carbon source 8.0mgCOD / mgTN, and expected nitrate nitrogen value at the outlet of the last anoxic stage 10mg / L were collected and sent to the automatic control system.

[0095] Step S3: The automatic control system calculates the nitrate nitrogen removal capacity (N) in the anoxic zone based on the collected data. W计 And the required carbon source addition amount Q 碳 .

[0096] Nitrate removal capacity in the anoxic zone (N) W计 :

[0097] N W计 =K*M L1 *V1=5040g / h;

[0098] The required amount of nitrate nitrogen (N) to be removed in the anoxic section W需 :

[0099] NW需 =Q*(C N1 -C N0 = 6000g / h;

[0100] Required carbon source addition Q 碳 :

[0101] Q 碳 =1000*M W0 *(C N1 -C N0 )*Q / Nc+1000*γ*K C *M L3 *V2

[0102] / Nc=277.8L / h;

[0103] The safety factor γ is set to 0.2.

[0104] Step S4: Determine the control strategy based on the data, and adjust the carbon source dosage and activated sludge dosage through the control module.

[0105] Determine N W计 <N W需 This indicates that the amount of activated sludge in the anoxic zone is insufficient, and more activated sludge needs to be added. The amount of activated sludge to be added is Q. 泥 Calculation formula:

[0106] Target sludge concentration value M L目 The calculation formula is as follows:

[0107] M L目 =Q*(C N1 -C N0 K / V1 = 5000 mg / L;

[0108] According to M L目 Calculate the amount of activated sludge added, Q. 泥 :

[0109] Q 泥 =(QM L1 -QM L目 ) / (M L目 -M L2 ) = 47m 3 / h;

[0110] The wastewater treatment plant adjusted the activated sludge dosage in the anoxic zone to 47m³. 3After adjusting the carbon source dosage to 277.8 L / h, the sludge concentration in the anoxic tank reached 5000 mg / L. At this point, the nitrate nitrogen value in the effluent from the anoxic tank was 9.7 mg / L, slightly lower than the expected value, while the total nitrogen value was 12.1 mg / L and the COD value was 25.8 mg / L, meeting the effluent discharge requirements. Given the relatively stable influent conditions and collection range of the wastewater treatment plant, carbon source denitrification and COD degradation experiments were conducted twice daily. Due to the complex composition of the composite carbon source, these experiments were performed each time a new batch of carbon source was introduced to determine the new carbon source denitrification rate and COD degradation rate.

[0111] The original carbon source dosage method at this wastewater treatment plant was adjusted based on the total nitrogen in the effluent, with a daily target of 12 mg / L. When the total nitrogen in the effluent was high, the carbon source dosage was increased; when the total nitrogen in the effluent was low, the dosage was decreased. Recently, due to high influent total nitrogen, the effluent total nitrogen was also high. To reduce the effluent total nitrogen, the wastewater treatment plant continuously increased the carbon source dosage from 250 L / h to 500 L / h. However, the reduction in effluent total nitrogen was minimal, while the effluent COD increased significantly. When the carbon source dosage reached 500 L / h, the effluent COD exceeded the discharge limit. The results show that simply increasing the carbon source dosage cannot effectively reduce effluent total nitrogen; instead, it easily leads to excessive effluent COD. The specific adjustments to the original carbon source and the water quality results at this wastewater treatment plant are shown in the table below:

[0112] TN (mg / L) of effluent 15.4 14.4 14.0 13.7 Effluent COD (mg / L) 26.4 28.6 40.4 53.2

[0113] Example 2

[0114] A wastewater treatment plant uses a four-stage AO process with a treatment capacity of 48,000 tons / day. The carbon source is added at the final anoxic stage, which has a volume of 4000 m³. 3 The final aerobic section has a volume of 4000 m³. 3 The external reflux rate is 100%, the sludge concentration is 3500 mg / L, the designed influent COD concentration is 450 mg / L, the total nitrogen concentration is 55 mg / L, and the ammonia nitrogen concentration is 50 mg / L. The effluent complies with local standards, with COD emission limits of 30 mg / L and TN emission limits of 10 mg / L. The carbon source used in the plant is a composite carbon source with a COD equivalent of 600,000 mg / L.

[0115] The denitrification control method for the anoxic zone of the biological tank in a wastewater treatment plant includes the following steps: Step S1: Conduct a carbon source denitrification experiment using a denitrification experimental system. Take 50L of activated sludge from the anoxic zone inlet and add it to the experimental container (total volume 70L). Record the initial COD value (18.2mg / L), nitrate nitrogen value (12.4mg / L), and sludge concentration of 3600mg / L. Add a carbon source to conduct the denitrification experiment. The amount of carbon source added (C / N=5) is 5mL. Record the COD value after adding the carbon source (78.3mg / L). Stop the experiment after reaching the set reaction time and record the COD value (36.3mg / L) and nitrate nitrogen value (5.4mg / L). The reaction time is the actual residence time of the anoxic zone.

[0116] The residence time H = V / Q = 1 hour, and the reaction time is 1 hour.

[0117] Denitrification rate K N Calculation formula:

[0118] K N =(C N1 -C N2 ) / M LN / H=0.0019mgNO3-N / (mgMLSS·h);

[0119] Carbon source denitrification nitrogen removal ratio M W0 Calculation formula:

[0120] M W0 =(C C1 -C C2 ) / (C N1 -C N2 = 6.0 mg COD / mg TN;

[0121] A carbon source COD degradation experiment was conducted using a carbon source experimental system. 50L of activated sludge from the anoxic section outlet was added to the experimental container (total volume 70L), and the initial COD value (16.7mg / L) was recorded. The carbon source was then added to carry out the COD degradation experiment. The amount of carbon source added was 2.5mL, and the COD value after adding the carbon source was recorded (46.5mg / L). The experiment was conducted after 1 hour, and the COD value was recorded (15.4mg / L).

[0122] Carbon source COD degradation rate Kc:

[0123] Kc=(C C1 -C C2 ) / M LC / H = 0.0086 mg COD / (mg MLSS·h)

[0124] Step S2: Collect the influent flow rate Q of the anoxic section, which is 4000 m³ / h. 3 / h, hypoxic zone volume V1 value 4000m 3 aerobic section volume V2 value 4000m³ 3 , Sludge concentration M in the anoxic section L1 Value 3600mg / L, aerobic sludge concentration M L3 Value 3600mg / L, sludge concentration M in sludge thickening tank L2 Value 18000 mg / L, nitrate nitrogen concentration C in the influent of the anoxic section N1 Value 12.5 mg / L, denitrification rate K N The values ​​of NO3-N / (mgMLSS·h), COD degradation rate Kc value of carbon source 0.0086mgCOD / (mgMLSS·h), carbon source denitrification-to-nitrification ratio 6.0mgCOD / mgTN, and expected nitrate nitrogen value at the outlet of the last anoxic stage 6.0mg / L were collected and sent to the automatic control system.

[0125] Step S3: The automatic control system calculates the nitrate nitrogen removal capacity (N) in the anoxic zone based on the collected data. W计 And the required carbon source addition amount Q 碳 .

[0126] Nitrate removal capacity in the anoxic zone (N) W计 :

[0127] N W计 =K*M L1 *V1=27360g / h;

[0128] The required amount of nitrate nitrogen (N) to be removed in the anoxic section W需 :

[0129] N W需 =Q*(C N1 -C N0 = 26000 g / h;

[0130] Required carbon source addition Q 碳 :

[0131] Q 碳 =1000*M W0 *(C N1 -C N0 )*Q / Nc+1000*γ*K C *M L3 *V2

[0132] / Nc=321.9L / h;

[0133] The safety factor γ is set to 0.3.

[0134] Step S4: Determine the control strategy based on the data, and adjust the carbon source dosage and activated sludge dosage through the control module.

[0135] Determine N W计 ≥N W需 This indicates that the amount of activated sludge in the anoxic zone is sufficient, and there is no need to add more activated sludge. At this time, only a carbon source needs to be added.

[0136] After adjusting the carbon source dosage to 321.9 L / h, the nitrate nitrogen value in the effluent from the anoxic tank was 5.7 mg / L, the total nitrogen value was 6.4 mg / L, and the COD value was 16.8 mg / L, meeting the effluent discharge requirements.

[0137] Because the wastewater treatment plant receives some industrial water from the industrial park, the influent water quality fluctuates greatly. Carbon source denitrification and COD degradation experiments are conducted four times a day. At the same time, due to the complex composition of the composite carbon source, carbon source denitrification and COD degradation experiments are conducted each time a new batch of carbon source is replaced to determine the new carbon source denitrification rate and COD degradation rate.

[0138] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling denitrification in the anoxic section of a biological treatment plant, characterized in that: Includes the following steps: Step S1: Conduct carbon source denitrification and carbon source COD degradation experiments using a carbon source experimental system, and calculate the denitrification rate K of the sludge. N Carbon source denitrification nitrogen removal ratio M W0 and COD degradation rate Kc; Step S2: Collect the influent flow rate Q of the anoxic section, the volume V1 of the anoxic section, the volume V2 of the aerobic section, and the sludge concentration M of the anoxic section. L1 , Sludge concentration M in sludge thickening tank L2 aerobic sludge concentration M L3 1. Nitrate nitrogen concentration C in the influent of the anoxic section N1 ; Step S3: Calculate the removal amount N of nitrate nitrogen in the anoxic zone based on the calculation results of Step S1 and the parameters collected in Step S2. W计 The amount of nitrate nitrogen (N) that needs to be removed in the anoxic section W需 ; Step S4: Calculate N based on step S3. W计 and N W需 Adjust the amount of carbon source and activated sludge added; The adjustment operation in step S4 is as follows: When N W计 ≥N W需 When the amount of activated sludge in the anoxic zone is sufficient, there is no need to add more activated sludge; at this time, only a carbon source needs to be added. When N W计 <N W需 If the amount of activated sludge in the anoxic zone is insufficient, more activated sludge needs to be added. The formula for calculating the amount of carbon source added is as follows: Q 碳 =1000 M W0 (C N1 -C N0 ) Q / N C + 1000 γ K C M L3 V2 / N C Among them, Q 碳 The amount of carbon source added is expressed in L / h; N C γ is the carbon source COD equivalent, in g / L; γ is the safety factor, ranging from 0.1 to 0.5; M L3 V1 is the concentration of activated sludge at the front end of the aerobic tank, in mg / L; V2 is the volume of the aerobic section, in m³. 3 M L3 C represents the sludge concentration in the aerobic zone, in mg / L. N1 The concentration of nitrate nitrogen in the influent of the anoxic section is expressed in mg / L; C N0 The expected nitrate nitrogen value at the outlet of the anoxic section is expressed in mg / L. And / or, the formula for calculating the dosage of the activated sludge is: Q 泥 =(QM L1 -QM L目 ) / (M L目 -M L2 ); Among them, Q 泥 This refers to the amount of activated sludge added, in cubic meters (m³). 3 / h;M L目 Q represents the target sludge concentration in the anoxic zone, in mg / L; Q represents the influent flow rate in the anoxic zone, in m³ / s. 3 / h;M L2 Sludge concentration M in sludge thickening tank L2 The unit is mg / L; M L1 The concentration of sludge in the anoxic zone is expressed in mg / L. Target sludge concentration M in the anoxic section L目 The calculation formula is: M L目 =Q (C N1 -C N0 ) / K N / V1 Where Q is the influent flow rate of the anoxic section, in m³ / s. 3 / h; K N V1 is the denitrification rate, expressed in mgNO3-N / (mgMLSS·h); V1 is the volume of the anoxic zone, expressed in m³. 3 .

2. The method for controlling denitrification in the anoxic section of a biological treatment plant as described in claim 1, characterized in that: The denitrification rate K in step S1 N The calculation formula is: K N =(C N1 -C N2 ) / M LN / H Among them, K N C represents the denitrification rate of carbon source, expressed in mgNO3-N / (mgMLSS·h); N1 The concentration of nitrate nitrogen before the experiment is expressed in mg / L; C N2 M represents the nitrate nitrogen concentration after the experiment, in mg / L. LN The concentration of activated sludge in the carbon source denitrification experiment is in mg / L; H is the reaction time in hours.

3. The method for controlling denitrification in the anoxic section of a biological treatment plant as described in claim 1, characterized in that: In step S1, the carbon source denitrification nitrogen removal ratio M W0 The calculation formula is: M W0 =(C C1 -C C2 ) / (C N1 -C N2 ) Among them, M W0 The carbon source denitrification nitrogen removal ratio is the amount of COD consumed to remove a unit of nitrate nitrogen, expressed in mgCOD / mgTN; C C1 The initial COD concentration after adding the carbon source is expressed in mg / L; C C2 COD concentration after the experiment, in mg / L; C N1 The concentration of nitrate nitrogen before the experiment is expressed in mg / L; C N2 This represents the concentration of nitrate nitrogen after the experiment, in mg / L.

4. The method for controlling denitrification in the anoxic section of a biological treatment plant as described in claim 1, characterized in that: The formula for calculating the COD degradation rate Kc in step S1 is as follows: Kc=(C C3 -C C4 ) / M LC / H Among them, K C The carbon source represents the aerobic COD degradation rate, expressed in mgCOD / (mgMLSS•h). C3 The COD concentration before the carbon source COD degradation experiment is expressed in mg / L; C C4 M represents the COD concentration after the carbon source COD degradation experiment, in mg / L. LC The concentration of activated sludge in the COD degradation experiment is mg / L; H is the reaction time in hours.

5. The method for controlling denitrification in the anoxic section of a biological treatment plant as described in claim 1, characterized in that: In step S3, N W计 The calculation formula is as follows: N W计 =K N M L1 V1 Where, N W计 Calculate the removal rate of nitrate nitrogen in the anoxic zone, in g / h; K N V1 is the denitrification rate, expressed in mgNO3-N / (mgMLSS·h); V1 is the volume of the anoxic zone, expressed in m³. 3 M L1 The concentration of sludge in the anoxic zone is expressed in mg / L. And / or, in step S3, N W需 The calculation formula is as follows: N W需 =Q (C N1 -C N0 ) Where, N W需 The amount of nitrate nitrogen to be removed in the anoxic zone, expressed in g / h; C N0 The expected nitrate nitrogen value at the outlet of the anoxic section, in mg / L; C N1 Q represents the nitrate nitrogen concentration in the influent to the anoxic section, in mg / L; Q represents the influent flow rate to the anoxic section, in m³ / s. 3 / h.

6. The method for controlling denitrification in the anoxic section of a biological treatment plant as described in claim 1, characterized in that: When M L目 When the value exceeds the maximum value of the secondary sedimentation tank, the sludge concentration is adjusted according to the maximum value. If the nitrate nitrogen in the effluent of the anoxic section still does not meet the expected value, the carbon source is replaced. The maximum value of the secondary sedimentation tank is determined by the wastewater treatment plant based on the actual operation of the secondary sedimentation tank.

7. A control device for implementing the denitrification control method in the anoxic section of a biological treatment tank in a wastewater treatment plant according to any one of claims 1-6, characterized in that: The device includes: The online monitoring system is used to monitor in real time the influent flow rate of the anoxic zone, the nitrate nitrogen concentration of the influent of the anoxic zone, the sludge concentration of the anoxic zone, the sludge concentration of the sludge thickener, the carbon source dosage, and the sludge dosage, and sends these parameters to the automatic control system. The carbon source experimental system is used to detect the denitrification rate and denitrification nitrogen removal ratio of the carbon source, and send the denitrification rate and denitrification nitrogen removal ratio to the automatic control system. The automatic control system is used to determine the carbon source reagent and sludge addition adjustment method based on the influent flow rate of the anoxic zone, the nitrate nitrogen concentration of the influent of the anoxic zone, the sludge concentration of the anoxic zone, the carbon source denitrification rate, and the denitrification ratio, and to send reagent addition control signals and activated sludge addition control signals.

8. The control device according to claim 7, characterized in that: The carbon source experimental system includes a denitrification experimental container, a carbon source COD degradation experimental container, an electric stirrer, a filter, a vacuum sludge pump, an aeration disc, and a blower. The upper part of the experimental container is equipped with a volume-fixing port for fixed-volume activated sludge; the bottom is equipped with a drain port for emptying the container after the experiment. During the experiment, the vacuum sludge pump extracts activated sludge from the front and back of the anoxic section. Avoid stirring and breaking up the sludge mixture, which would damage the sludge flocs and make the experimental sludge more accurately reflect the state of the activated sludge in the anoxic section. And / or, the automatic control system includes a control module and a display module. The control module is connected to the electric stirrer, the return sludge pump, the COD sampling pump, the vacuum sludge pump, the dosing pump, the blower, and the display module, respectively. The control module controls the operation of each component and performs data processing. The display module is connected to the online detection system. The display module enables the operator to input control information for the equipment and display the detection results. The display module includes an input device and a display. And / or, the online detection system includes an instantaneous flow meter, an online nitrate nitrogen meter, an online sludge concentration meter, an online COD detector, an online flow meter, and an online dissolved oxygen meter; The instantaneous flow meter is used to measure the instantaneous flow rate of the influent in the anoxic section; The online nitrate nitrogen meter is used to detect the nitrate nitrogen content in the influent of the anoxic section and the nitrate nitrogen content in the activated sludge solution of the denitrification experiment, respectively. The online sludge concentration meter is used to detect the sludge concentration in the anoxic zone, the sludge concentration in the activated sludge solution of the denitrification experiment, the sludge concentration in the thickening tank, the sludge concentration in the mixed liquor of the carbon source COD degradation experiment, and the sludge concentration at the inlet of the aerobic tank. The online COD detector is used to detect COD; The online flow meters are used to detect the amount of carbon source added and the amount of activated sludge added, respectively. The online dissolved oxygen meter is used to detect dissolved oxygen in the sludge mixture of the carbon source COD degradation experiment and to detect dissolved oxygen in the aerobic tank.

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