A smart dosing method for nitrogen and phosphorus removal in wastewater

Abstract

This invention discloses an intelligent dosing method for nitrogen and phosphorus removal in wastewater, belonging to the fields of energy conservation and carbon reduction and wastewater treatment technology. The method is based on the ORP of the influent and effluent in the anoxic tank and the NO3 content of the influent. ‑ The concentration is calculated using a formula, and N dosing intervals are set, each corresponding to a different dosing concentration. The dosage is then calculated based on the raw water volume. The entire process requires no human intervention, only real-time monitoring of the raw water quality. The dosage can be automatically adjusted after changes in water quality, thereby achieving accurate, rapid, and convenient determination of carbon source dosage. This improves water treatment efficiency, reduces water treatment costs, and reduces the labor intensity of operators, achieving the goals of cost reduction, efficiency improvement, energy conservation, and carbon reduction.

Description

Technical Field

[0001] This invention relates to an intelligent dosing method for nitrogen and phosphorus removal in wastewater, belonging to the fields of energy conservation, carbon reduction, and wastewater treatment technology. Background Technology

[0002] Nitrogen and phosphorus removal involves multiple biochemical processes, including nitrification, denitrification, and phosphorus release and desorption. Each process has a different purpose and different requirements for microbial composition, substrate type, and environmental conditions. Therefore, simultaneously completing nitrogen and phosphorus removal processes in a single system inevitably leads to conflicting relationships between these processes, such as carbon source, sludge age, nitrate, nitrification and denitrification capacity, and phosphorus release and uptake capacity. Denitrifying bacteria and polyphosphate-accumulating bacteria play two independent roles in nitrogen and phosphorus removal processes, respectively. Both require organic carbon sources for independent denitrification and phosphorus uptake and desorption, thus inevitably leading to competition for carbon sources within the same system.

[0003] Currently, there are three main methods for carbon source addition in urban wastewater treatment plants: constant dosage, manual adjustment, and automatic dosage. Among these, constant dosage is used for adding carbon sources to the effluent total nitrogen (TN) (including NO3). - When NH3 and other pollutants do not exceed the standard, the carbon source dosage is basically not adjusted, and the dosage is relatively large. Manual adjustment is generally based on the total nitrogen (TN) meter reading of the effluent, which has a large lag and often results in over- or under-dosing. Moreover, the effluent TN is unstable and often faces the risk of exceeding the standard. Automatic dosing is generally based on time-series control and advanced algorithms to predict dosing, but time-series control has a large lag, and existing advanced algorithms still rely on the effluent TN concentration for automatic dosing, resulting in a large dosage.

[0004] Therefore, it is necessary to develop an intelligent dosing method that is easy to operate and implement, can improve the stability of the effluent, reduce dosing costs, and improve the precision of operation and management. Summary of the Invention

[0005] [Technical Issues]

[0006] The amount of carbon source added in wastewater treatment plants is unstable and has a large lag, resulting in a large waste of carbon sources and an increase in carbon emissions.

[0007] [Technical Solution]

[0008] This invention is based on the oxidation-reduction potential (ORP) of the influent and effluent in the anoxic tank, and the NO3 content of the influent. - The concentration is calculated using a formula, and N dosing intervals are set, each corresponding to a different dosing concentration. The dosage is then calculated based on the volume of the raw water.

[0009] To ensure the stability of the dosage, the number of dosage intervals can be set by the user; the more intervals, the more precise the dosage.

[0010] This invention solves the problem of "unstable carbon source addition in wastewater treatment plants with a large lag, resulting in a large waste of carbon sources and increased carbon emissions".

[0011] Specifically, firstly, based on the difference in oxidation-reduction potential between the influent and effluent of the anoxic tank... ORP (-300 mV ~ 0 mV) allows for the setting of N dosing intervals, with NO3 added through the anoxic tank. - Data collected from concentration meters and influent / effluent ORP meters; the ORP of the influent to the anoxic tank is obtained by subtracting the ORP of the effluent from the anoxic tank ORP. ORP (Optimal Reduction Process) is used to calculate the average dosing concentration for each dosing interval. NO3 is then added to the influent of the anoxic tank. - The concentration is compared with the baseline value (8 mg / L), and the carbon source dosage is calculated in conjunction with the raw water volume. After determining the dosage, the dosing pump can be turned on to add the chemical, and the PID automatic adjustment is performed based on the dosing flow rate collected by the dosing flow meter to ensure accurate dosing.

[0012] The purpose of this invention is to provide an intelligent dosing method for nitrogen and phosphorus removal in wastewater. This method is applied in an intelligent control system for nitrogen and phosphorus removal in wastewater and includes the following steps:

[0013] Step 1: Based on the difference in oxidation-reduction potential between the influent and effluent of the anoxic tank. ORP (-300 mV ~ 0 mV) allows users to set N dosing intervals, each corresponding to a different dosing concentration;

[0014] Step 2: Install ORP online instruments at the inlet and outlet of the anoxic tank, and install NO3 at the inlet of the anoxic tank. - Online instruments and carbon source dosing points are located inside the anaerobic tank;

[0015] Step 3: Obtain the NO3 concentration in the current anoxic tank influent. - The concentration is determined based on the difference in oxidation-reduction potential between the influent and effluent of the anoxic tank corresponding to each dosing zone. NO3 in the anoxic tank influent - To calculate the average dosage concentration for each dosing interval: First, calculate the redox potential difference corresponding to each dosing interval using the following formula. The endpoint values ​​are used to calculate the corresponding dosage concentration. Then, the redox potential difference corresponding to each dosing interval is... The dosage concentrations corresponding to the two endpoint values The average concentration of the drug [COD] is obtained by summing and averaging.

[0016] (1)

[0017] in:

[0018] Dosage concentration, mg / L (as COD concentration);

[0019] [NO3 - NO3 in the anoxic tank influent - Concentration, mg / L (as N);

[0020] ORP: ORP 缺氧池进水 -ORP 缺氧池出水 The range is -300 mV to 0 mV.

[0021] Obtain the current ORP of the influent and effluent from the anoxic tank to determine the specific dosing concentration.

[0022] Step 4: Based on the current raw water flow rate, calculate the carbon source dosage according to formula (2):

[0023] (2)

[0024] in:

[0025] M: Carbon source dosage, kg / h;

[0026] n: compensation coefficient, NO3 - When the concentration is ≤8 mg / L, n takes the value 1, NO3 - When the concentration is >8 mg / L, n takes the value of 2;

[0027] [COD]: Average dosage concentration, mg / L (as COD concentration);

[0028] Q: Raw water flow rate, m 3 / h;

[0029] a: COD equivalent value, dimensionless.

[0030] Step 5: After determining the dosage, the dosing pump can be turned on to add the pesticide. The PID automatic adjustment is performed based on the dosing flow rate collected by the dosing flow meter to ensure accurate dosing.

[0031] Step Six: The intelligent dosing method for nitrogen and phosphorus removal in wastewater further includes: collecting the ORP of the influent and effluent of the anoxic tank and the NO3 of the influent of the anoxic tank at each dosing time. - The concentration was determined, and a training set was established. The training set was used for machine learning. The constant in formula (1) was adjusted, and the carbon source dosage was calculated according to the adjusted formula.

[0032] [Beneficial Effects]

[0033] By adopting the above-mentioned technical solution, this invention has the following advantages and positive effects compared with the prior art: This invention sets up multiple dosing intervals, each with a corresponding dosing concentration, and then determines the dosing amount based on the water volume. The entire process requires no human intervention, only real-time monitoring of the raw water quality and quantity. It can automatically adjust the dosing amount after changes in water quality, thereby achieving accurate, fast, and convenient determination of carbon source dosage, improving water treatment efficiency, reducing water treatment costs, reducing the labor intensity of operators, and achieving the goals of cost reduction, efficiency improvement, energy conservation, and carbon reduction. Attached Figure Description

[0034] Figure 1 This is a flowchart of an intelligent dosing method for nitrogen and phosphorus removal in wastewater according to the present invention.

[0035] Figure 2 This is a schematic diagram of the intelligent dosing system for nitrogen and phosphorus removal in wastewater according to the present invention; wherein, 1. Carbon source dissolution device; 2. Carbon source dosing pump; 3. Carbon source dosing flow meter; 4. Anaerobic tank; 5. Anoxic tank; 6. Aerobic tank; 7. Mixed liquor return pump; 8. Mixed liquor return flow meter; 9. ORP instrument for anoxic tank influent; 10. NO3 influent to anoxic tank. - Instruments; 11. ORP instrument for effluent from the anoxic tank; 12. Intelligent dosing system; 13. PLC control cabinet for carbon source dosing; 14. Influent to the denitrification and phosphorus removal reaction tank; 15. Effluent from the denitrification and phosphorus removal reaction tank.

[0036] Figure 3 This is a distribution diagram of the average dosage of chemicals used in the present invention for nitrogen and phosphorus removal in wastewater.

[0037] Figure 4A This is a diagram illustrating the effect of carbon source dosing in a wastewater treatment plant using manual dosing methods.

[0038] Figure 4B This diagram illustrates the effect of carbon source dosage in a wastewater treatment plant using the method described in this application. Detailed Implementation

[0039] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0040] Example 1

[0041] This embodiment provides an intelligent dosing method for nitrogen and phosphorus removal in wastewater, applied to wastewater nitrogen and phosphorus removal systems, such as... Figure 2As shown, the wastewater denitrification and phosphorus removal system includes a carbon source dissolving device 1, a denitrification and phosphorus removal reaction tank, a carbon source dosing PLC control cabinet, and an intelligent dosing system 12. The carbon source dissolving device 1 is used to fully dissolve the added carbon source. The intelligent dosing system 12 is used to determine a certain dosing strategy based on the relevant indicators in the denitrification and phosphorus removal reaction tank, and then feeds it back to the carbon source dosing PLC control cabinet so that the carbon source dosing PLC control cabinet can add the fully dissolved carbon source in the carbon source dissolving device 1 to the denitrification and phosphorus removal reaction tank according to the dosing strategy.

[0042] like Figure 2 As shown, the denitrification and phosphorus removal reactor includes an anaerobic tank 4, an anoxic tank 5, and an aerobic tank 6 connected in sequence. A carbon source dissolution device 1 is connected to the anaerobic tank 4 by a carbon source dosing pump 2 and a carbon source dosing flow meter 3. The carbon source dosing PLC control cabinet controls the carbon source dosing amount via the carbon source dosing flow meter 3. In the denitrification and phosphorus removal reactor, ORP meters are installed at both the inlet and outlet of the anoxic tank 5, designated as anoxic tank inlet ORP meter 9 and anoxic tank outlet ORP meter 11, respectively. Additionally, a NO3- meter is installed at the inlet of the anoxic tank 5. - The instrument, recorded as NO3 in the influent of the anoxic tank. - Instrument 10; ORP meter for anoxic tank influent; Instrument 9; NO3 meter for anoxic tank influent. - Instrument 10 and ORP instrument 11 for the effluent from the anoxic tank are both connected to the intelligent dosing system 12 to transmit the acquired ORP value and NO3 value of the influent to the anoxic tank. - The values ​​of the influent and effluent ORP from the anoxic tank are fed back to the intelligent dosing system 12. The intelligent dosing system 12 then adjusts the dosing based on the ORP values ​​of the influent and effluent from the anoxic tank and the NO3 content of the influent. - The value determines the amount of carbon source added.

[0043] In this embodiment, acetic acid (COD equivalent a = 1.07) is used as the carbon source for illustration. Figure 1 As shown, the method is as follows:

[0044] Step 1: Based on the difference in oxidation-reduction potential between the influent and effluent of the anoxic tank. ORP is set with N dosing intervals;

[0045] In this embodiment, N is set to 5, according to The ORP range (-300 mV ~ 0 mV) corresponds to 5 dosing intervals, as follows:

[0046] The criterion for determining dosing interval 1 is: influent / effluent -300 mV ≤ ORP≤-240 mV;

[0047] The criterion for determining the dosing interval 2 is: -240 mV < ORP≤-180 mV;

[0048] The criterion for determining the dosing interval 3 is: -180 mV < ORP≤-120 mV;

[0049] The criterion for determining the dosing interval 4 is: -120 mV < ORP≤-60 mV;

[0050] The criterion for determining the dosing interval 5 is: -60 mV < ORP≤0 mV.

[0051] Step 2: Collect the ORP values ​​of the influent and effluent of the anoxic tank, and calculate the oxidation-reduction potential difference between the influent and effluent of the anoxic tank. ORP determines the dosing zone to which it belongs;

[0052] like Figure 2 As shown, the ORP meter 9 for the anoxic tank influent and the NO3 meter for the anoxic tank influent are... - Instrument 10 is installed at the inlet of the anoxic tank, and ORP instrument 11 is installed at the outlet of the anoxic tank. The data detected online is collected to the intelligent dosing system 12 through the signal line.

[0053] The subsequent intelligent dosing system 12 processes the collected data (including the ORP values ​​of the influent and effluent of the anoxic tank and the NO3 content of the influent) according to the method of the present invention. - The value is analyzed and calculated, and then the final dosage is fed back to the carbon source dosing PLC control cabinet. The PLC controls the flow rate through the carbon source dosing flow meter 3, thereby controlling the carbon source dosing amount.

[0054] Step 3: Collect NO3 from the anoxic pool - The value is based on the difference in oxidation-reduction potential between the influent and effluent of the anoxic tank corresponding to each dosing interval. NO3 in the anoxic tank influent - To calculate the average dosage concentration for each dosing interval: First, calculate the redox potential difference corresponding to each dosing interval using the following formula. The endpoint values ​​are used to calculate the corresponding dosage concentration. Then, the redox potential difference corresponding to each dosing interval is... The dosage concentrations corresponding to the two endpoint values The average concentration of the drug [COD] is obtained by summing and averaging.

[0055] (1)

[0056] in: Indicates the dosage concentration, mg / L (as COD concentration); [NO3] - [Indicates NO3 in the influent of the anoxic tank]- Concentration, mg / L (as N); ORP represents the difference in oxidation-reduction potential between the influent and effluent of anoxic tanks. ORP=ORP 缺氧池进水 -ORP 缺氧池出水 The range is -300 mV to 0 mV.

[0057] For example: Obtaining NO3 from the influent of anoxic ponds - The concentration is 5 mg / L. Calculate the average dosage concentration for each dosing interval:

[0058] The criterion for determining dosing interval 1 is: influent / effluent -300 mV ≤ ORP ≤ -240 mV, average dosage concentration: 7.23 mg / L;

[0059] The criterion for determining the dosing interval 2 is: -240 mV < ORP ≤ -180 mV, average dosage concentration: 8.31 mg / L;

[0060] The criterion for determining the dosing interval 3 is: -180 mV < ORP ≤ -120 mV, average dosage concentration: 9.39 mg / L;

[0061] The criterion for determining the dosing interval 4 is: -120 mV < ORP ≤ -60 mV, average dosage concentration: 10.47 mg / L;

[0062] The criterion for determining the dosing interval 5 is: -60 mV < ORP≤0 mV, average drug concentration: 11.55 mg / L.

[0063] The current ORP values ​​for the influent and effluent of the anoxic tank are -400 mV and -200 mV, respectively. With an ORP of -200 mV and a dosing interval of 2 selected, the average dosing concentration was 8.31 mg / L.

[0064] For example: Obtaining NO3 from the influent of anoxic ponds - The concentration is 9 mg / L. Calculate the average dosage concentration for each dosing interval:

[0065] The criterion for determining dosing interval 1 is: influent / effluent -300 mV ≤ ORP ≤ -240 mV, average dosage concentration: 7.99 mg / L;

[0066] The criterion for determining the dosing interval 2 is: -240 mV < ORP ≤ -180 mV, average dosage concentration: 9.07 mg / L;

[0067] The criterion for determining the dosing interval 3 is: -180 mV < ORP ≤ -120 mV, average dosage concentration: 10.15 mg / L;

[0068] The criterion for determining the dosing interval 4 is: -120 mV < ORP ≤ -60 mV, average drug concentration: 11.23 mg / L;

[0069] The criterion for determining the dosing interval 5 is: -60 mV < ORP≤0 mV, average drug concentration: 12.31 mg / L.

[0070] The current ORP values ​​for the influent and effluent of the anoxic tank are -300 mV and -180 mV, respectively. With an ORP of -120 mV and a dosing interval of 3 selected, the average dosing concentration was 10.15 mg / L.

[0071] Step 4: Obtain the current flow rate of raw water and calculate the carbon source dosage according to formula (2);

[0072] (2)

[0073] Where M represents the carbon source dosage, kg / h; n represents the compensation coefficient, NO3 - When the concentration is ≤8 mg / L, n is 1; NO3 - When the concentration is >8 mg / L, n is 2; [COD] represents the average dosage concentration, mg / L (expressed as COD concentration); Q represents the raw water flow rate, m 3 / h; a represents the COD equivalent value, which is dimensionless, and the value in this example is 1.07.

[0074] For example, if the current raw water flow rate is 20,000 m³ / s. 3 / h, calculate the carbon source dosage according to formula (2).

[0075] Example 1: Obtaining NO3 from the influent of anoxic tank - If the concentration is 5 mg / L and the average dosage is 8.31 mg / L, then the acetic acid dosage is 155 kg / h.

[0076] Example 2: Obtaining NO3 from the influent of anoxic tank - If the concentration is 9 mg / L and the average dosage is 10.15 mg / L, then the acetic acid dosage is 379 kg / h.

[0077] Step 5: Accurately administer the medication according to the dosage calculated in Step 4;

[0078] After determining the dosage, the dosing pump can be turned on to add the pesticide. The PID automatic adjustment is performed based on the dosing flow rate collected by the dosing flow meter to ensure accurate dosing.

[0079] Figure 3 This is a distribution map of the average dosage for nitrogen and phosphorus removal in wastewater using the method described in this application, combined with... Figure 3 As can be seen from formula (1), With [NO3] - ]and The ORP changes accordingly, and the more dosing intervals you set yourself, the more accurate the average dosing concentration will be.

[0080] To illustrate the effectiveness of this application's solution, this embodiment compares the effects of manual dosing and the dosing method of this application, such as... Figure 4A and Figure 4B As shown, after adding a carbon source using the intelligent dosing method provided in this application, the NO3 in the effluent from the wastewater treatment plant is reduced. - The average concentration was 1.57 mg / L, a 56% reduction compared to manual dosing, and the average TP concentration in the effluent was 0.2 mg / L. The average influent flow over 30 days was 179,000 t / d. The average chemical consumption for manual and intelligent dosing was 0.38 t / 10,000 t / t of acetic acid and 0.21 t / 10,000 t / t of water, respectively. Using the intelligent dosing method of this invention, the carbon source dosage was reduced by 45%.

[0081] Therefore, the intelligent carbon source dosing method of the present invention can ensure the NO3 content in the effluent. - TP can achieve stable emissions that meet standards, while also greatly saving on carbon source input, reducing input costs and carbon emissions, and reducing the labor intensity of operators, thus achieving the goals of cost reduction, efficiency improvement, energy conservation, and carbon reduction.

[0082] Some steps in the embodiments of the present invention can be implemented using software, and the corresponding software program can be stored in a readable storage medium, such as an optical disc or a hard disk.

[0083] 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 smart dosing method for nitrogen and phosphorus removal in wastewater, characterized in that, The method includes: Step 1: Obtain the oxidation-reduction potential difference between the influent and effluent of the anoxic tank in the denitrification and phosphorus removal reactor. and according to N dosing zones are set up; the denitrification and phosphorus removal reaction tank is equipped with an anaerobic tank, an anoxic tank and an aerobic tank connected in this order. Step 2, collect NO3 from the influent of the anoxic tank. - The value is based on the difference in oxidation-reduction potential between the influent and effluent of the anoxic tank corresponding to each dosing interval. NO3 in the anoxic tank influent - The average dosage concentration for each dosing interval is calculated: Step 3: Obtain the current raw water flow rate and calculate the dosage using the following formula: Where M represents the carbon source dosage; n represents the compensation coefficient; [COD] represents the average dosage concentration; Q represents the raw water flow rate; and m 3 / h; a represents the COD equivalent value; Step 4: Add the corresponding carbon source to the anaerobic tank in the denitrification and phosphorus removal reaction tank according to the dosage calculated in Step 3; In step 2, the oxidation-reduction potential difference between the influent and effluent of the anoxic tank corresponding to each dosing interval is used. NO3 in the anoxic tank influent - When calculating the average dosage concentration for each dosing interval, first calculate the redox potential difference corresponding to each dosing interval using the following formula. The endpoint values ​​are used to calculate the corresponding dosage concentration. Then, the redox potential difference corresponding to each dosing interval is... The dosage concentrations corresponding to the two endpoint values The average concentration of the drug [COD] is obtained by summing and averaging: in, Indicates the concentration of the drug, expressed as COD concentration; [NO3] - [Indicates NO3 in the influent of the anoxic tank] - concentration; This represents the difference in oxidation-reduction potential between the influent and effluent of the anoxic tank. =ORP 缺氧池进水 -ORP 缺氧池出水 .

2. The method according to claim 1, characterized in that, In step 3, the compensation coefficient n takes the value of 1 or 2: When NO3 - When the concentration is ≤8 mg / L, the value of n is 1; When NO3 - When the concentration is >8 mg / L, the value of n is 2.

3. The method according to claim 2, characterized in that, The method further includes: Collect ORP from the influent and effluent of the anoxic tank at each dosing, and NO3 from the influent of the anoxic tank. - Concentration, combined with dosage, to establish a training set, use the training set for machine learning, adjust the constant in the average dosage concentration formula, and then calculate the average dosage concentration based on the adjusted formula.

4. The method according to claim 3, characterized in that, The method is applied to a wastewater denitrification and phosphorus removal system, which includes a carbon source dissolution device, a denitrification and phosphorus removal reaction tank, a carbon source dosing PLC control cabinet, and an intelligent dosing system. The carbon source dissolution device is used to fully dissolve the added carbon source. ORP meters are installed at both the inlet and outlet of the anoxic tank in the denitrification and phosphorus removal reaction tank to collect the ORP values ​​of the inlet and outlet water. An NO3- meter is also installed at the inlet of the anoxic tank. - Instruments are used to collect NO3 in the influent of the anoxic tank. - Value; The intelligent dosing system is used to determine the ORP values ​​of the influent and effluent of the anoxic tank and the NO3 content of the influent. - The value determines the amount of carbon source to be added, and then feeds it back to the carbon source addition PLC control cabinet so that the carbon source addition PLC control cabinet can add the fully dissolved carbon source in the carbon source dissolution device to the anaerobic tank of the denitrification and phosphorus removal reaction tank according to the amount of carbon source to be added.

5. The method according to claim 1, characterized in that, A mixed liquor return pump is installed between the effluent from the aerobic tank and the influent from the anoxic tank, which allows the effluent from the aerobic tank to flow back to the influent from the anoxic tank.

6. The method according to claim 4, characterized in that, The carbon source addition PLC control cabinet uses a PID control strategy when adding carbon source according to the carbon source addition amount.

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