Denitrification nitrogen removal control method and device for anoxic zone of biological tank of sewage treatment plant

Abstract

The invention provides a denitrification nitrogen removal control method and device for an anoxic zone of a biological tank of a sewage treatment plant, and the method comprises the following steps: carrying out a carbon source denitrification experiment and a carbon source COD (Chemical Oxygen Demand) degradation experiment by utilizing a carbon source experiment system, and calculating the denitrification rate, the carbon source denitrification nitrogen removal ratio and the COD degradation rate of sludge; the method comprises the following steps: collecting anoxic section water inlet flow, anoxic section volume, aerobic section volume, anoxic section sludge concentration, sludge concentration of a sludge concentration tank, aerobic section sludge concentration and anoxic section water inlet nitrate nitrogen concentration; calculating the calculation removal amount of the nitrate nitrogen in the anoxic zone and the amount of the nitrate nitrogen needing to be removed in the anoxic zone; and adjusting the adding amount of the carbon source and the adding amount of the activated sludge. The carbon source adding amount and the sludge adding amount are determined according to the actual denitrification nitrogen removal rate, the nitrogen removal ratio and other data of the anoxic section of the biological tank of the sewage treatment plant, the nitrogen removal effect of the anoxic section is improved, and the total nitrogen discharge requirement of the water quality of the sewage treatment plant is met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sewage treatment, and particularly relates to a method and device for controlling denitrification in an anoxic section of a biological tank of a sewage treatment plant. BACKGROUND

[0002] Under anoxic conditions, the denitrifying bacterial flora in the anoxic section of the biological tank of the sewage treatment plant utilizes organic matter to carry out denitrification, removes nitrate nitrogen in the sewage, and achieves the purpose of denitrogenation. Factors such as sludge activity, sludge quantity, and carbon source dosage affect the denitrogenation effect in the anoxic section. At present, the problem of low C / N of influent water exists universally in urban sewage treatment plants in China, which leads to insufficient carbon source required for denitrification in the biological tank, and limits the denitrogenation effect. At the same time, the discharge requirement of effluent TN of the sewage treatment plant is getting higher and higher, and many local standards have already required TN≤10 mg / L. In order to meet the requirement of effluent TN, external carbon source needs to be added to improve the denitrogenation efficiency.

[0003] The existing technology mainly focuses on the screening method and intelligent dosing control method of carbon source. The carbon source dosage is often calculated according to the empirical denitrification ratio (C / N=4-6:1) or the theoretical denitrification ratio (C / N=2.86:1). However, there is a large difference between the calculated value and the actual value, and there is a large difference in denitrification ratio between different types of carbon sources and different properties of activated sludge. For example, in the patent CN 114538612A, a kind of precise dosing system of external carbon source and its control method is provided. The system accurately controls the carbon source dosage in a combination of feedforward and feedback based on the nitrate nitrogen load of influent water in the anoxic section and the nitrate nitrogen concentration of effluent water.

[0004] However, in the actual operation of the sewage treatment plant, the denitrification efficiency of different carbon sources and the carbon source utilization rate of activated sludge are different. If the amount of activated sludge in the anoxic section, the amount of organic matter, and the adaptability of microorganisms to organic matter are not considered, and only the carbon source dosage is increased, when the amount of activated sludge in the biological tank is insufficient, the added carbon source cannot be completely degraded within the residence time, which not only does not effectively reduce the total nitrogen but also causes the effluent COD to exceed the standard, and the actual effect does not reach the expected target. SUMMARY

[0005] The denitrification of sewage treatment plant is that the nitrate is reduced to nitrogen by the denitrification bacteria under the anoxic environment in the anoxic section, and then the denitrification effect is realized. The denitrification capacity in the anoxic section is directly related to the carbon source denitrification rate, the activated sludge concentration and the residence time, wherein the carbon source denitrification rate is mainly related to the carbon source type, the substrate concentration and the adaptability of the activated sludge microorganism. In order to control the denitrification in the anoxic section of the sewage treatment plant, the nitrate nitrogen value of the effluent in the anoxic section meets the requirements, and the effluent COD is avoided to exceed the standard. In view of this, the present application aims at overcoming the defects in the prior art, and provides a sewage treatment plant biological pool anoxic section denitrification control method and device. The present application can effectively control the denitrification effect in the anoxic section of the sewage treatment plant biological pool, adjust the carbon source and activated sludge addition in the anoxic section, improve the denitrification effect in the anoxic section, and meet the discharge standard of the sewage treatment plant.

[0006] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0007] In the first aspect, the present application provides a sewage treatment plant biological pool anoxic section denitrification control method, comprising the following steps:

[0008] Step S1: carbon source denitrification experiment and carbon source COD degradation experiment are carried out by using a carbon source experiment system, and the denitrification rate K of the sludge, the carbon source denitrification denitrification ratio M and the COD degradation rate Kc are calculated. N W0

[0009] Step S2: the anoxic section influent flow Q, the anoxic section volume V1, the aerobic section volume V2, the anoxic section sludge concentration M L1 , the sludge concentration M L2 of the sludge thickening tank, the aerobic section sludge concentration M L3 , and the anoxic section influent nitrate nitrogen concentration C N1 are collected.

[0010] Step S3: the calculated results of step S1 and the collected parameters of step S2 are used to calculate the anoxic section nitrate nitrogen removal amount N W计 and the anoxic section nitrate nitrogen amount N W需 to be removed.

[0011] Step S4: according to the calculation of step S3, N W计 and N W需 are obtained, and the carbon source addition amount and the activated sludge addition amount are adjusted.

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

[0013] K N = (C N1 -C N2 ) / M​​LN / H

[0014] wherein, K N is the carbon source denitrification nitrogen removal rate, in mgNO3-N / (mgMLSS h); C N1 is the nitrate nitrogen concentration before the experiment, in mg / L; C N2 is the nitrate nitrogen concentration after the experiment, in mg / L; M LN is the carbon source denitrification experimental activated sludge concentration, in mg / L; and H is the reaction time, in hours.

[0015] In some embodiments, the carbon source denitrification nitrogen removal ratio M W0 in step S1 is calculated according to the following formula:

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

[0017] wherein, M W0 is the carbon source denitrification nitrogen removal ratio, i.e., the amount of COD consumed per unit of nitrate nitrogen removed, in mgCOD / mgTN; C C1 is the initial COD concentration after adding the carbon source, in mg / L; C C2 is the COD concentration after the experiment, in mg / L; C N1 is the nitrate nitrogen concentration before the experiment, in mg / L; and C N2 is the nitrate nitrogen concentration after the experiment, in mg / L.

[0018] In some embodiments, the COD degradation rate Kc in step S1 is calculated according to the following formula:

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

[0020] wherein, K C is the carbon source aerobic COD degradation rate, in mgCOD / (mgMLSS h), C C3 is the COD concentration before the carbon source COD degradation experiment, in mg / L; C C4 is the COD concentration after the carbon source COD degradation experiment, in mg / L; M LC is the carbon source COD degradation experimental activated sludge concentration, in mg / L; and H is the reaction time, in hours.

[0021] In some embodiments, the N W计The calculation formula of N is as follows:

[0022] N W计 = K N * M L1 * V1

[0023] Wherein, N W计 is the calculated removal amount of nitrate nitrogen in the anoxic section, in g / h; K N is the denitrification rate, in mgNO3-N / (mgMLSS·h); V1 is the volume of the anoxic section, in m 3 ; M L1 is the sludge concentration in the anoxic section, in mg / L.

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

[0025] N W需 = Q*(C N1 -C N0 )

[0026] Wherein, N W需 is the amount of nitrate nitrogen that needs to be removed in the anoxic section, in g / h; C N0 is the expected nitrate nitrogen value at the outlet of the anoxic section, in mg / L; C N1 is the nitrate nitrogen concentration of the influent of the anoxic section, in mg / L; Q is the influent flow rate of the anoxic section, in m 3 / h;

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

[0028] When N W计 ≥ N W需 , it indicates that the amount of activated sludge in the anoxic section is sufficient, and no activated sludge needs to be added, at this time, only carbon source needs to be added;

[0029] When N W计 < N W需 , it indicates that the amount of activated sludge in the anoxic section is insufficient, and activated sludge needs to be added.

[0030] In some embodiments, the calculation formula of the addition amount of the carbon source is as follows:

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

[0032] Wherein, Q 碳is the dosage of carbon source, unit: L / h; N C is the COD equivalent of carbon source, unit: g / L; γ is the safety factor, value 0.1-0.5; M L3 is the activated sludge concentration at the front end of the aerobic tank, unit: mg / L; V2 is the volume of the aerobic section, unit: m 3 ; M L3 is the sludge concentration in the aerobic section, unit: mg / L.

[0033] In some embodiments, the calculation formula of the dosage of activated sludge is:

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

[0035] Wherein, Q 泥 is the dosage of activated sludge, unit: m 3 / h; M L目 is the target sludge concentration in the anoxic section, unit: mg / L; Q is the influent flow rate of the anoxic section, unit: m 3 / h; M L2 is the sludge concentration M L2 in the sludge thickening tank, unit: mg / L; M L1 is the sludge concentration in the anoxic section, unit: mg / L;

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

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

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

[0039] In some embodiments, when the value of M L目 exceeds the maximum value of the secondary sedimentation tank, M L最大(the sewage treatment plant determines according to the actual operation of the secondary sedimentation tank), the sludge concentration is adjusted according to the maximum value, and if the nitrate nitrogen of the effluent in the anoxic section still does not meet the expected value at this time, the carbon source is replaced.

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

[0041] In a second aspect, the present application also provides a device for controlling denitrification in the anoxic section of a biological tank of a sewage treatment plant, which comprises:

[0042] An online detection system for detecting the influent quantity of the anoxic section, the nitrate nitrogen concentration of the influent of the anoxic section, the sludge concentration of the anoxic section, the sludge concentration of the sludge thickening tank, the carbon source dosage, and the sludge dosage in real time, and sending these parameters to the automatic control system;

[0043] A carbon source experiment system for detecting the denitrification rate and the denitrification ratio of the carbon source, and sending the denitrification rate and the denitrification ratio to the automatic control system;

[0044] An automatic control system for determining the carbon source agent and the sludge dosage adjustment method according to the influent quantity of the anoxic section, the nitrate nitrogen concentration of the influent of the anoxic section, the sludge concentration of the anoxic section, the carbon source denitrification rate, and the denitrification ratio, and sending the agent dosage control signal and the activated sludge dosage control signal.

[0045] In some embodiments, the carbon source experiment system comprises a denitrification experiment container, a carbon source COD degradation experiment container, an electric stirrer, a filter, a vacuum sludge pump, an aeration disc, and a fan; the upper part of the experiment container is provided with a constant volume port for constant volume of activated sludge; the bottom is provided with a liquid discharge port for emptying the container after the experiment; the activated sludge at the front end and the tail end of the anoxic section is extracted by the vacuum sludge pump during the experiment; the stirring and dispersion of the sludge mixed liquid are avoided, the sludge flocculation body is destroyed, and the sludge used in the experiment more accurately reflects the state of the activated sludge in the anoxic section.

[0046] In some embodiments, the automatic control system comprises a control module and a display module, the control module is connected with the electric stirrer, the return sludge pump, the COD sampling pump, the vacuum sludge pump, the dosing pump, the fan, and the display module, the control module controls the work of each component and performs data processing; the display module is connected with the online detection system, the display module realizes the input of control information of the equipment by the operator and the display of detection results, and the display module comprises an input device and a display.

[0047] In some embodiments, the online detection system comprises an instantaneous flowmeter, an online nitrate nitrogen measuring instrument, an online sludge concentration meter, an online COD detector, an online flowmeter, and an online dissolved oxygen meter,

[0048] The instantaneous flowmeter is used for measuring the instantaneous flow of the influent of the anoxic section.

[0049] The online nitrate nitrogen measuring instrument is respectively used for detecting the nitrate nitrogen content of the influent in the anoxic section and detecting the nitrate nitrogen content of the denitrification experimental activated sludge solution;

[0050] The online sludge concentration meter is respectively used for detecting the sludge concentration in the anoxic section, detecting the sludge concentration of the denitrification experimental activated sludge solution, detecting the sludge concentration in the concentration tank, detecting the sludge concentration of the sludge mixed solution in the carbon source COD degradation experiment and detecting the sludge concentration at the inlet of the aerobic tank;

[0051] The online COD detector is used for detecting COD;

[0052] The online flow meter is respectively used for detecting the online flow meter of the carbon source dosing amount and detecting the activated sludge dosing amount;

[0053] The online dissolved oxygen meter is respectively used for detecting the dissolved oxygen of the sludge mixed solution in the carbon source COD degradation experiment and detecting the dissolved oxygen in the aerobic tank.

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

[0055] The present application determines the denitrification capacity of the anoxic section through the denitrification experiment of the activated sludge in the anoxic section, determines the theoretical denitrogenation amount of the anoxic section according to the denitrification rate, the volume of the anoxic section and the sludge concentration, calculates the actual nitrate nitrogen amount required to be removed in the anoxic section through the nitrate nitrogen concentration of the influent in the anoxic section and the target concentration value, and adjusts the sludge dosing amount and the carbon source dosing amount after comparing the theoretical denitrogenation amount of the anoxic section with the actual nitrate nitrogen amount required to be removed.

[0056] The present application solves the problem that the effluent COD exceeds the standard due to the blind addition of the carbon source in the sewage treatment plant, and determines the dosing amount of the carbon source or the dosing amount of the activated sludge according to the actual denitrification denitrogenation capacity of the carbon source, so that the amount of the activated sludge and the amount of the organic matter in the anoxic section meet the denitrogenation condition, the dosing amount of the carbon source is more accurate, the denitrogenation effect in the anoxic section is improved, the total nitrogen emission requirement of the water quality in the sewage treatment plant is met, and the present application has great application value. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 It is a structure schematic view of the denitrification and denitrogenation control device for the anoxic section of the biological tank of the sewage treatment plant.

[0058] Figure 2 It is a flow schematic view of the denitrification and denitrogenation control method for the anoxic section of the biological tank of the sewage treatment plant.

[0059] MARKS OF THE DRAWINGS:

[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 meter; 7, 18 - online flow meter; 8 - dosing pump; 9, 23 - denitrification experiment vessel; 10, 24 - filter; 11 - online COD detector; 12, 27 - vacuum sludge pump; 13, 25 - COD sampling pump; 14 - electric agitator; 15 - reflux sludge pump; 16, 19 - constant volume port; 17, 20 - liquid discharge port; 21 - fan; 22 - aeration disc; 30 - online dissolved oxygen meter. DETAILED DESCRIPTION

[0061] Embodiments of the present application are described in detail below. The embodiments described below are examples only and are not intended to limit the present application.

[0062] In the present text, 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 belongs.

[0063] In the present text, where values are described as ranges, it is to be understood that the disclosure includes disclosure of all possible sub-ranges within the range, and of the specific values falling within the range, regardless of whether the specific values or the specific sub-ranges are explicitly indicated.

[0064] In the present text, reference to "a plurality of" or the like, without further qualification, means two or more, or equal to two. For example, "one or more" means one or more than one.

[0065] In the present text, reference to "preferably", "more preferably" is only for the purpose of describing embodiments or examples that are better than others, and it is understood that it does not constitute a limitation to the scope of protection of the present application.

[0066] In the present text, reference to "further" or the like is for the purpose of description, indicating a difference in content, but it is not to be understood as a limitation to the scope of protection of the present application.

[0067] In the present text, the term "and / or" is a descriptive association of objects, indicating that there can be three relationships. For example, A and / or B, means: A or B, or A and B, the three relationships.

[0068] In the present text, the term "about" means + / - 10% of the specified value, preferably + / - 5%, more preferably + / - 1%.

[0069] In the present text, "comprising", "including", "having", "containing", and the like, are all open terms, i.e. meaning including but not limited to.

[0070] 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, unless indicated otherwise. Although preferred methods and materials are described, any method and material similar or equivalent to those described herein can be used in the practice or testing of the present application.

[0071] The present application provides a device for controlling denitrification in the anoxic zone of a biological tank in a sewage treatment plant, as shown in the figure, which comprises: Figure 1

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

[0073] The online detection system is used to detect the influent quantity 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 thickening tank, the carbon source dosage, and the sludge dosage, and send these parameters to the automatic control system.

[0074] The carbon source experiment 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 and sludge dosage strategy according to the influent quantity 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 the dosage control signal and the activated sludge dosage control signal.

[0076] Specifically, the online detection system comprises a flow meter 3 for measuring the instantaneous flow of the influent of the anoxic zone, an online nitrate nitrogen measuring instrument 1 for detecting the nitrate nitrogen content of the influent of the anoxic zone, an online sludge concentration meter 2 for detecting the sludge concentration of the anoxic zone, an online nitrate nitrogen instrument 4 for detecting the nitrate nitrogen of the activated sludge solution in the denitrification experiment, an online sludge concentration meter 5 for detecting the sludge concentration of the activated sludge solution in the denitrification experiment, an online sludge concentration meter 6 for detecting the sludge concentration of the thickening tank, an online COD detector 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 instrument 26 for detecting the dissolved oxygen of the sludge mixed solution in the carbon source COD degradation experiment, an online sludge concentration meter 29 for detecting the sludge concentration of the sludge mixed solution in 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 instrument 30 for detecting the dissolved oxygen of the aerobic tank.

[0077] ​The carbon source experiment system comprises a denitrification experiment container 9, a carbon source COD degradation experiment container 23, an electric agitator 14, a filter 10, vacuum sludge pumps 12 and 27, an aeration disc 22 and a fan 21. The experiment containers 9 and 23 are respectively provided with constant-volume openings 16 and 19 at the upper portions for constant-volume of activated sludge, and are respectively provided with liquid discharge openings 17 and 20 at the bottom portions for emptying the containers after the experiment. The activated sludge at the front end and the end of the anoxic section is respectively extracted by the vacuum sludge pumps 12 and 27 during the experiment, so as to avoid stirring and scattering of the sludge mixed liquid, to destroy the sludge flocculation body, and to make the sludge used in the experiment more accurately reflect the state of the activated sludge in the anoxic section.

[0078] The automatic control system comprises a control module and a display module. The control module is connected with the electric agitator 14, the reflux sludge pump 15, the COD sampling pumps 13 and 25, the vacuum sludge pumps 12 and 27, the dosing pump 8, the fan 21 and the display module, and controls the working of each component and performs data processing. The display module is connected with the online detection system, and realizes input of control information of the equipment by the operator and display of the detection results. The display module comprises an input device and a display.

[0079] The application will be described in detail in combination with the following examples. The methods in the following Example 1 and Example 2 both use the above device.

[0080] Example 1

[0081] A sewage treatment plant adopts a three-stage AO process, and the treatment capacity is 12,000 tons / day. The carbon source is added at the last anoxic section, the volume of the last anoxic section is 1,000 m 3 , the external reflux is 100%, the sludge concentration is 4,000 mg / L, the volume of the last aerobic section is 1,000 m 3 , the design of the influent COD concentration is 400 mg / L, the total nitrogen concentration is 50 mg / L, the ammonia nitrogen concentration is 40 mg / L, and the effluent executes the first level A standard in the "Urban Sewage Treatment Plant Pollutant Discharge Standard" (GB 18918-2002). The carbon source used in the plant is a composite carbon source, and the COD equivalent is 200,000 mg / L.

[0082] The denitrification and nitrogen removal control method for the anoxic section of the biological tank of the sewage treatment plant comprises the following steps:

[0083] Step S1: carbon source denitrification experiment was carried out by using carbon source experiment system, 50L of activated sludge from the inlet of anoxic section was added into the experimental container (total volume 70L), the initial nitrate nitrogen value (16.6mg / L) and sludge concentration (4200mg / L) were recorded, carbon source was added for denitrification experiment, the adding amount of composite carbon source (C / N=5) was 20mL, the COD value (115.4mg / L) after adding carbon source was recorded, the experiment was stopped after reaching the set reaction time, the COD value (75.3mg / L) and nitrate nitrogen value (11.6mg / L) were recorded, and the reaction time was the actual residence time of the anoxic section.

[0084] The stirrer was started, the sludge sampling pump (rated flow 10L / min, effective volume of the experimental container 70L) was started, the sampling electromagnetic valve was opened, and activated sludge from the front end of the anoxic section (before the carbon source adding point) was continuously fed into the experimental container, the sampling electromagnetic valve was closed after reaching the overflow liquid level. The value displayed by the online nitrate nitrogen instrument at this time was read, the stirring motor speed was controlled to maintain the mixed state in the experimental container. 20ml of composite carbon source was added, the water sampling pump of the online COD detection device was started, and the initial COD value was detected.

[0085] The actual residence time of the anoxic section H=V1 / Q=1 hour, the carbon source experiment reaction time was 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 )=8mgCOD / mgTN;

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

[0091] Start the stirrer, start the sludge sampling pump (rated flow 10 L / min, effective volume of the bioreactor tank 70 L), open the sampling electromagnetic valve, continuously feed the activated sludge from the outlet end of the anoxic section into the experimental container, after reaching the liquid level of the overflow, close the sampling electromagnetic valve. Open the bottom aeration, read the dissolved oxygen in the experimental container, control the fan to keep the dissolved oxygen in the container consistent with the dissolved oxygen in the aerobic section. Add 10 ml of composite carbon source, start the water sampling pump of the online COD detection device, and detect the initial COD value.

[0092] Carbon source COD degradation rate Kc:

[0093] Kc = (C C1 -C C2 ) / M LC / H = 0.009 mgCOD / (mgMLSS·h);

[0094] Step S2: Collect the anoxic section influent flow rate Q value 1000 m 3 / h, the anoxic section volume V1 value 1000 m 3 , the aerobic section volume V2 value 1000 m 3 , the anoxic section sludge concentration M L1 value 4200 mg / L, the aerobic section sludge concentration M L3 value 4200 mg / L, the sludge thickener sludge concentration M L2 value 22000 mg / L, the anoxic section influent nitrate nitrogen concentration C N1 value 16 mg / L, the denitrification rate K N value 0.0012 mgNO3-N / (mgMLSS·h), the carbon source COD degradation rate Kc value 0.009 mgCOD / (mgMLSS·h), the carbon source denitrification single removal ratio 8.0 mgCOD / mgTN, the expected value of the last stage anoxic section effluent nitrate nitrogen 10 mg / L, and send the collected data to the automatic control system.

[0095] Step S3: The automatic control system calculates the anoxic section nitrate nitrogen removal capacity N W计 and the required carbon source dosage Q 碳 according to the collected data.

[0096] Anoxic section nitrate nitrogen removal capacity N W计 :

[0097] N W计 = K*M L1 *V1 = 5040 g / h;

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

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

[0100] Required carbon source dosage Q 碳 :

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

[0102] / Nc = 277.8 L / h;

[0103] Where the safety factor γ is 0.2.

[0104] Step S4: According to the data to determine the control strategy, adjust the carbon source dosage and activated sludge dosage through the control module.

[0105] Determine N W计 < N W需 , indicating that the amount of activated sludge in the anoxic section is not enough, and activated sludge needs to be added, and the activated sludge dosage Q 泥 The calculation formula is:

[0106] The 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 , the activated sludge dosage Q 泥 is calculated:

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

[0110] The activated sludge dosage in the anoxic section of the sewage plant is adjusted to 47 m 3After the carbon source dosage was adjusted to 277.8 L / h, the sludge concentration in the anoxic tank reached 5000 mg / L, at which time the nitrate nitrogen value in the anoxic tank effluent was 9.7 mg / L, which was slightly lower than the expected value, the total nitrogen in the effluent was 12.1 mg / L, and the COD value was 25.8 mg / L, meeting the effluent discharge requirements. According to the influent conditions and the change of the effluent range of the sewage plant, carbon source denitrification and COD degradation experiments were carried out twice a day. Since the composition of the composite carbon source is complex, carbon source denitrification and COD degradation experiments are carried out every time a new batch of carbon source is replaced to determine the new carbon source denitrification rate and COD degradation rate.

[0111] The original carbon source dosage method of the sewage plant is adjusted according to the total nitrogen in the effluent, and the daily control target value is 12 mg / L. When the total nitrogen in the effluent is high, the carbon source dosage is increased, and when the total nitrogen in the effluent is low, the carbon source dosage is decreased. In recent years, due to the high total nitrogen in the influent, the total nitrogen in the effluent is also high. In order to reduce the total nitrogen in the effluent, the sewage plant continuously increases the carbon source dosage to reduce the total nitrogen, from 250 L / h to 500 L / h, but the total nitrogen in the effluent is reduced very little, and the COD in the effluent is increased by a large margin. When the carbon source dosage is 500 L / h, the COD in the effluent exceeds the discharge limit. From the results, it can be seen that simply increasing the carbon source dosage cannot effectively reduce the total nitrogen in the effluent, but can easily cause the COD in the effluent to exceed the standard. The original carbon source adjustment and water quality results of the sewage plant are as follows:

[0112] Carbon source amount (L / h) 240 300 400 500 Effluent TN (mg / L) 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 sewage treatment plant uses a four-stage AO process, with a treatment capacity of 48,000 tons / day. The carbon source is added at the last stage of the anoxic section, and the volume of the last anoxic section is 4000 m 3 , the volume of the last aerobic section is 4000 m 3 , the external reflux is 100%, the sludge concentration is 3500 mg / L, the design 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 meets the local standard, of which the COD discharge limit is 30 mg / L and the TN discharge limit is 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 control method for denitrification in the anoxic section of a biological tank of a sewage treatment plant comprises the following steps: Step S1: carbon source denitrification experiment is conducted by using a denitrification experiment system, 50 L of activated sludge at the inlet of the anoxic section is taken and added into an experiment container (total volume 70 L), the initial COD value (18.2 mg / L), nitrate nitrogen value (12.4 mg / L) and sludge concentration (3600 mg / L) are recorded, carbon source is added for denitrification experiment, the carbon source addition amount (C / N=5) is 5 mL, the COD value (78.3 mg / L) after the addition of the carbon source is recorded, the experiment is stopped after the set reaction time, the COD value (36.3 mg / L) and the nitrate nitrogen value (5.4 mg / L) are recorded, and the reaction time is the actual residence time of the anoxic section.

[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=0.0019 mg NO3-N / (mg MLSS·h);

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

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

[0121] Carbon source COD degradation experiment is conducted by using a carbon source experiment system, 50 L of activated sludge at the outlet of the anoxic section is taken and added into an experiment container (total volume 70 L), the initial COD value (16.7 mg / L) is recorded, carbon source is added for COD degradation experiment, the carbon source addition amount is 2.5 mL, the COD value (46.5 mg / L) after the addition of the carbon source is recorded, and the experiment is conducted for 1 hour, and the COD value (15.4 mg / L) is recorded.

[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: the influent flow Q of the anoxic section is 4000 m 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: According to the data, the control strategy is determined, and the carbon source and activated sludge dosing amounts are adjusted by the control module.

[0135] Determination N W计 ≥N W需 , indicating that the amount of activated sludge in the anoxic section is sufficient, and there is no need to add activated sludge. At this time, only carbon source needs to be added.

[0136] After adjusting the carbon source dosing amount to 321.9 L / h in the sewage plant, the effluent nitrate nitrogen value of the anoxic tank is 5.7 mg / L, the total nitrogen value is 6.4 mg / L, and the COD value is 16.8 mg / L, meeting the effluent discharge requirements.

[0137] Since the sewage plant receives industrial water from part of the industrial park, the fluctuation of the influent water quality is large. Carbon source denitrification and COD degradation experiments are performed 4 times a day. In addition, since the composition of the composite carbon source is complex, carbon source denitrification and COD degradation experiments are performed 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 only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

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.

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), 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 expressed in mg / L; H represents 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: 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.

7. The method for controlling denitrification in the anoxic section of a biological treatment plant as described in claim 6, characterized in that: 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 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 This refers to the sludge concentration in the aerobic section, 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;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 .

8. 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.

9. A denitrification control device for the anoxic section of a biological treatment plant, 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.

10. The denitrification control device for the anoxic section of the biological treatment tank in a wastewater treatment plant according to claim 9, 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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