Water quality ammonia nitrogen on-line monitoring system and detection method thereof

Abstract

The invention relates to the technical field of water quality monitoring, and discloses a water quality ammonia nitrogen on-line monitoring system and a detection method thereof.The system comprises a sampling unit, a reagent storing and adding unit, a reaction unit, a detection unit, a control processing unit and a cleaning unit; a standardized detection process is established, so that the reliability of ammonia nitrogen detection under different water quality conditions is ensured; the color development state change in the reaction process is monitored in real time through an automatic system, reagent activity abnormity and environmental interference factors can be recognized in real time, the problem of detection deviation caused by reagent instability and operation errors in a traditional method is solved, the accuracy of ammonia nitrogen concentration detection is improved, and the environmental monitoring risk is reduced; by dynamically analyzing the influence degree of environmental parameter change on a detection result, the stability and accuracy of ammonia nitrogen concentration detection under a complex water quality condition are ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water quality monitoring, in particular to a water quality ammonia nitrogen online monitoring system and a detection method thereof. BACKGROUND

[0002] Ammonia nitrogen, as a major pollutant exceeding the standard, appears very frequently in the seven water systems. Ammonia nitrogen pollution is a nationwide pollution problem. Excessive ammonia nitrogen can lead to water eutrophication, causing water to become black and smelly, and destroying the ecological balance of aquatic life. Ammonia nitrogen in water can be converted into nitrite under certain conditions, which is harmful to human health if consumed for a long time.

[0003] At present, in the process of water quality ammonia nitrogen detection, the traditional laboratory method is relied on. When real-time monitoring of the ammonia nitrogen concentration of water samples is carried out, the chemical reagents used contain toxic substances and the color reaction needs to be waited for a long time, which cannot meet the demand of online continuous monitoring. When the activity of the reagent is reduced due to changes in storage conditions during the detection process, human errors are introduced by manual operation, which can cause the ammonia nitrogen concentration determination result to deviate from the actual value, and cannot guarantee the timeliness and accuracy of water quality safety early warning.

[0004] Therefore, the present application provides a water quality ammonia nitrogen online monitoring system and a detection method thereof to solve the above problems. SUMMARY

[0005] (1) Technical problem solved In view of the deficiencies of the prior art, the present application provides a water quality ammonia nitrogen online monitoring system and a detection method thereof, which solves the problems raised in the background art.

[0006] (2) Technical scheme In order to achieve the above purpose, the present application provides the following technical scheme: a water quality ammonia nitrogen online monitoring system and a detection method thereof, comprising the following steps: S1, collecting water samples to be tested and pretreating to remove suspended matter interference; S2, adding an optimized formula of color developing agent and oxidizing agent to the water sample, wherein the color developing agent comprises 130g of sodium salicylate, 130g of sodium citrate, 1.5g of sodium nitrosoferricyanide and 300g of deionized water; The oxidizing agent comprises 6.4g of sodium hydroxide, 2g of sodium dichloroisocyanurate and 200g of deionized water; S3, transferring the water sample after adding reagents to a constant temperature reaction device, and performing color reaction under the condition of 37 degrees Celsius, and the reaction time is 20 minutes; S4, after the reaction is completed, the absorbance of the water sample is measured at a wavelength of 640 nanometers using a spectrophotometer; S5, calculating the ammonia nitrogen concentration in the water sample according to the absorbance based on a pre-established standard curve, the standard curve being established by measuring the absorbance of a plurality of standard solutions with known ammonia nitrogen concentrations at 640 nanometers, the correlation coefficient being not less than 0.9999; S6, outputting the ammonia nitrogen concentration data and performing real-time storage and transmission to a monitoring platform.

[0007] Preferably, the pretreatment in step S1 comprises: Removing particulate matter with a particle size greater than 0.45 microns from the water sample through an automatic filtering device, and adjusting the pH value of the water sample to the range of 7.0-7.5 in real time using a pH adjuster; Wherein, the filtering device adopts a multi-stage filter core structure, including a pre-coarse filter with a pore size of 5 microns and a final fine filter with a pore size of 0.45 microns, to enhance the removal efficiency of suspended solids; The pH adjuster is 0.1M hydrochloric acid, which is dynamically injected through a PID controller to ensure that the pH stability is within the range of ±0.1, thereby eliminating ion interference and improving the consistency of the color reaction.

[0008] Preferably, the specific preparation method of the color developing agent is: Dissolving sodium salicylate, potassium sodium tartrate, and sodium nitroprusside in deionized water according to the mass concentration ratio to form a mixed solution, and adding a stabilizer to extend the shelf life of the reagent; Wherein, the mass concentration ratio is defined by the following formula: ; Wherein represents the mass concentration of sodium salicylate, represents the mass concentration of potassium sodium tartrate, represents the mass concentration of sodium nitroprusside; The stabilizer is disodium ethylenediaminetetraacetate, and the addition amount is 0.1% of the total mass of the color developing agent, and after preparation, it is stored in a 4 dark place to maintain the activity of the reagent for more than 30 days.

[0009] Preferably, the specific preparation method of the oxidizing agent is: Dissolving sodium hydroxide and sodium dichloroisocyanurate in deionized water according to the molar concentration ratio to form a solution, and then adding an antioxidant to prevent the decomposition of sodium hypochlorite; Wherein, the molar concentration ratio of sodium hydroxide to sodium dichloroisocyanurate is 2:1, and the antioxidant is ascorbic acid, and the addition amount is 0.05% of the total mass of the oxidizing agent; During preparation, the solution temperature is controlled at 25±2 The mixture was then stirred at 300 rpm for 10 minutes using a magnetic stirrer to ensure uniformity and stability, thereby avoiding detection errors caused by oxidant degradation.

[0010] Preferably, the constant temperature reaction device in step S3 uses a PID temperature controller with a temperature control accuracy of ±0.5 degrees Celsius. Furthermore, the reaction time is adaptively adjusted based on the turbidity of the water sample: when the turbidity sensor detects that the turbidity of the water sample is higher than 50 NTU, the reaction time is automatically extended to 12 minutes; When the turbidity is below 50 NTU, the reaction time is maintained at 10 minutes; This adjustment is achieved through an embedded algorithm, covering a turbidity measurement range of 0-100 NTU with a resolution of 1 NTU, to compensate for light scattering interference in high-turbidity water samples, ensuring sufficient color development and accurate absorbance.

[0011] Preferably, the system includes: The sampling unit automatically collects water samples and performs preprocessing. The reagent storage and addition unit includes a colorimetric reagent storage tank, an oxidant storage tank, and a precision dispensing pump, for storing and adding the colorimetric reagent and oxidant of the optimized formulation; The reaction unit, including a temperature control device and a reaction vessel, carries out a colorimetric reaction at 40 degrees Celsius; The detection unit, including a spectrophotometer and a wavelength selector, is configured to measure absorbance at a wavelength of 640 nanometers. The control and processing unit is connected to each unit, and controls the operation sequence, processes absorbance data, calculates ammonia nitrogen concentration, and outputs the results. The cleaning unit automatically cleans itself after testing to prevent cross-contamination. The cleaning solution is a 0.1% sodium hypochlorite solution, and the cleaning cycle is performed after each test.

[0012] Preferably, the sampling unit includes: An automatic sampling pump periodically collects water samples. The sampling frequency can be set from 1 to 60 minutes per sample, and the sampling volume is calibrated via a flow meter with an accuracy of ±0.5 mL. The pretreatment module includes a filter and a pH adjuster. The filter uses a 0.45-micron pore size membrane to remove suspended solids and is equipped with a backwashing function to extend the membrane life. The pH regulator uses dilute hydrochloric acid (0.1M) to adjust the pH of the water sample to 7.0-7.5 in real time. The pH sensor has an accuracy of ±0.05, and the data is fed back to the PLC controller to achieve closed-loop control.

[0013] Preferably, the reagent storage and addition unit further includes: Multiple independent reagent containers, each storing colorimetric reagent, oxidant, and cleaning solution, are made of corrosion-resistant glass, have a capacity of 1L, and are equipped with a level sensor with an accuracy of ±10mL. The dispensing pump is a precision peristaltic pump driven by a stepper motor, with a dispensing accuracy of ±0.1 mL and a flow rate range of 0.1-5 mL / s; The reagent status monitoring sensor monitors the reagent level and stability in real time, including an optical sensor to detect changes in reagent color and an audible and visual alarm to warn of reagent failure.

[0014] Preferably, the temperature control device for the reaction unit includes: PTC heating element, temperature sensor: accuracy ±0.1 With a PID controller, the temperature control range is 30-50 degrees Celsius, the accuracy is ±0.5 degrees Celsius, and the response time is less than 30 seconds; The reaction vessel is made of quartz, has a volume of 10 ml, and is equipped with a stirrer with an adjustable speed range of 100-500 rpm to accelerate reagent mixing; The container is designed to be detachable for easy cleaning and maintenance, and integrates a temperature compensation algorithm to adapt to ambient temperature fluctuations: -10 Up to 50 .

[0015] Preferably, the control processing unit includes: The microprocessor runs an algorithm that calculates ammonia nitrogen concentration based on absorbance data and a standard curve. The calculation formula is as follows: ; in Indicates ammonia nitrogen concentration. This indicates the absorbance measured at a wavelength of 697 nm. and The coefficients of the standard curve are determined through periodic calibration; the correlation coefficient is also mentioned. Furthermore, calibration data is stored in non-volatile memory; The data module, including a display screen, data storage device, and wireless transmitter, displays concentration values ​​in real time, stores historical data with a capacity of ≥1 year, and transmits it to the cloud platform; The adaptive calibration module automatically adjusts the detection parameters based on the ambient temperature by acquiring water quality parameters through a temperature sensor. This includes dynamically optimizing the standard curve coefficients to ensure that the detection accuracy is within ±5% of the error range.

[0016] (III) Beneficial Effects Compared with the prior art, the present invention provides an online monitoring system and detection method for ammonia nitrogen in water quality, which has the following beneficial effects: 1. In this invention, when conducting online monitoring of ammonia nitrogen in water quality, the formulation and ratio parameters of the colorimetric reagent and oxidant are optimized, and a standardized detection process is established to ensure the reliability of ammonia nitrogen detection under different water quality conditions. By using an automated system to monitor the changes in the colorimetric state during the reaction process in real time, abnormal reagent activity and environmental interference factors can be identified in real time. This solves the detection deviation problem caused by reagent instability and operational errors in traditional methods, improves the accuracy of ammonia nitrogen concentration detection, and reduces environmental monitoring risks.

[0017] 2. In this invention, when performing online detection of ammonia nitrogen in water quality, the influence of changes in environmental parameters on the detection results is dynamically analyzed, and it is determined in real time whether interference factors such as temperature and turbidity exceed the tolerance range. When interference occurs, the system automatically triggers a compensation mechanism to adjust the detection parameters, so that the online monitoring process can adaptively correct the measurement deviation caused by environmental fluctuations, and ensure the stability and accuracy of ammonia nitrogen concentration detection under complex water quality conditions.

[0018] 3. In this invention, when conducting continuous monitoring of ammonia nitrogen in water quality, the detection signal is verified in multiple dimensions through a tiered data processing flow, including baseline calibration, outlier filtering, and result cross-validation; the system automatically outputs early warnings based on different confidence intervals, enabling the monitoring process to identify transient interference and real pollution events, improving the effectiveness of water quality safety assessment, and providing tiered decision support for environmental management. Attached Figure Description

[0019] Figure 1 This is a flowchart of an online method for detecting ammonia nitrogen in water according to the present invention; Figure 2 This is a schematic diagram of an online ammonia nitrogen monitoring system for water quality according to the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Specific embodiment: An online monitoring system for ammonia nitrogen in water quality and its detection method, comprising the following steps: S1. Collect the water sample to be tested and pre-treat it to remove interference from suspended solids; S2. Add the optimized formula of color developer and oxidant to the water sample, wherein the color developer includes 130g sodium salicylate, 130g sodium citrate, 1.5g sodium nitrosoferricyanide and 300g deionized water; The oxidizing agent consists of 6.4g sodium hydroxide, 2g sodium dichloroisocyanurate, and 200g deionized water; S3. Transfer the water sample after adding reagents to a constant temperature reaction apparatus and carry out a colorimetric reaction at 37 degrees Celsius for 20 minutes. S4. After the reaction is complete, use a spectrophotometer to measure the absorbance of the water sample at a wavelength of 640 nm. S5. Based on the pre-established standard curve, calculate the ammonia nitrogen concentration in the water sample according to the absorbance. The standard curve is established by measuring the absorbance of multiple standard solutions with known ammonia nitrogen concentrations at 640 nm, and the correlation coefficient is not less than 0.9999. S6. Output ammonia nitrogen concentration data and store and transmit it to the monitoring platform in real time.

[0022] The preprocessing in step S1 includes: The automatic filtration system removes particles larger than 0.45 micrometers from the water sample, and the pH value of the water sample is adjusted to the target range in real time using a pH adjuster. The adjustment amount is calculated using the following formula: ; in This is the volume of pH adjuster to be added. The target pH value is fixed at 7.25. The initial pH value of the water sample. For the volume of the water sample, As the concentration coefficient of the regulator, for 0.1M HCl / NaOH, k=0.35; The filtration device employs a multi-stage filter structure, including a pre-filter with a pore size of 5 microns and a final filter with a pore size of 0.45 microns, to enhance the removal efficiency of suspended solids. The pH adjuster is 0.1M hydrochloric acid, which is dynamically injected through a PID controller to ensure pH stability within ±0.1, thereby eliminating ion interference and improving the consistency of the colorimetric reaction.

[0023] The specific preparation method for the color developer is as follows: Sodium salicylate, potassium sodium tartrate, and sodium nitrosoferricyanide were dissolved in deionized water according to their mass concentration ratio to form a mixed solution, and a stabilizer was added to extend the shelf life of the reagent. The mass concentration ratio is defined by the following formula: ; in This indicates the mass concentration of sodium salicylate. This indicates the mass concentration of potassium sodium tartrate. This indicates the mass concentration of sodium nitrosoferricyanide; The stabilizer is disodium ethylenediaminetetraacetate, added at 0.1% of the total mass of the colorimetric reagent, and after preparation, it is set at 4... Store away from light to maintain reagent activity for more than 30 days; The accelerated aging test results for the reagent's shelf life are as follows: The specific preparation method for the oxidant is as follows: Sodium hydroxide and sodium dichloroisocyanurate were dissolved in deionized water at a molar concentration ratio, and their activity and stability were evaluated using the following formula: ; in The activity of the oxidant at time t. For initial activity, Storage time; when If the reagent is deemed ineffective, it needs to be replaced. Add 0.05% ascorbic acid antioxidant during preparation. After the solution is formed, an antioxidant is added to prevent the sodium hypochlorite from decomposing. The molar ratio of sodium hydroxide to sodium dichloroisocyanurate is 2:1, and the antioxidant is ascorbic acid, with an addition amount of 0.05% of the total mass of the oxidant. During preparation, the solution temperature is controlled at 25±2℃. The mixture was then stirred at 300 rpm for 10 minutes using a magnetic stirrer to ensure uniformity and stability, thereby avoiding detection errors caused by oxidant degradation.

[0024] The colorimetric reaction kinetics in step S3 satisfy: Reaction rate constant The relationship with temperature is determined by the Arrhenius equation: ; in The reaction rate constant is... As a pre-exponential factor, fixed at 1 / 2 , The activation energy is 45 kJ / mol. The gas constant is 8.314 J / mol·K. The reaction temperature; The constant temperature reaction device in step S3 uses a PID temperature controller with a temperature control accuracy of ±0.5 degrees Celsius. Furthermore, the reaction time is adaptively adjusted based on the turbidity of the water sample: when the turbidity sensor detects that the turbidity of the water sample is higher than 50 NTU, the reaction time is automatically extended to 12 minutes; When the turbidity is below 50 NTU, the reaction time is maintained at 10 minutes; This adjustment is achieved through an embedded algorithm, covering a turbidity measurement range of 0-100 NTU with a resolution of 1 NTU, to compensate for light scattering interference in high-turbidity water samples, ensuring sufficient color development and accurate absorbance.

[0025] The system includes: The sampling unit automatically collects water samples and performs preprocessing. The reagent storage and addition unit includes a colorimetric reagent storage tank, an oxidant storage tank, and a precision dispensing pump for storing and adding optimized formulations of colorimetric reagents and oxidants; The reaction unit, including a temperature control device and a reaction vessel, carries out a colorimetric reaction at 40 degrees Celsius; The detection unit, including a spectrophotometer and a wavelength selector, is configured to measure absorbance at a wavelength of 640 nanometers. The control and processing unit is connected to each unit, and controls the operation sequence, processes absorbance data, calculates ammonia nitrogen concentration, and outputs the results. The cleaning unit automatically cleans itself after testing to prevent cross-contamination. The cleaning solution is a 0.1% sodium hypochlorite solution, and the cleaning cycle is performed after each test.

[0026] The liquid addition accuracy of the sampling unit is verified by the following formula: ; in To allow for liquid addition error, This represents the actual volume of liquid added. To set the liquid addition volume; The peristaltic pump is controlled by a stepper motor, with a single-step resolution of 0.01 mL, ensuring the addition accuracy of color developer and oxidant is ±0.1 mL; The sampling unit includes: An automatic sampling pump periodically collects water samples. The sampling frequency can be set from 1 to 60 minutes per sample, and the sampling volume is calibrated via a flow meter with an accuracy of ±0.5 mL. The pretreatment module includes a filter and a pH adjuster. The filter uses a 0.45-micron pore size membrane to remove suspended solids and is equipped with a backwashing function to extend the membrane life. The pH regulator uses dilute hydrochloric acid (0.1M) to adjust the pH of the water sample to 7.0-7.5 in real time. The pH sensor has an accuracy of ±0.05, and the data is fed back to the PLC controller to achieve closed-loop control.

[0027] The reagent storage and addition unit also includes: Multiple independent reagent containers, each storing colorimetric reagent, oxidant, and cleaning solution, are made of corrosion-resistant glass, have a capacity of 1L, and are equipped with a level sensor with an accuracy of ±10mL. The dispensing pump is a precision peristaltic pump driven by a stepper motor, with a dispensing accuracy of ±0.1 mL and a flow rate range of 0.1-5 mL / s; The reagent status monitoring sensor monitors the reagent level and stability in real time, including an optical sensor to detect changes in reagent color and an audible and visual alarm to warn of reagent failure.

[0028] The temperature control stability of the reaction unit satisfies: ; in For temperature standard deviation, The number of sampling points. This represents the temperature value from the i-th sample. The temperature control device for the reaction unit includes: PTC heating element, temperature sensor: accuracy ±0.1 With a PID controller, the temperature control range is 30-50 degrees Celsius, the accuracy is ±0.5 degrees Celsius, and the response time is less than 30 seconds; The reaction vessel is made of quartz, has a volume of 10 ml, and is equipped with a stirrer with an adjustable speed range of 100-500 rpm to accelerate reagent mixing; The container is designed to be detachable for easy cleaning and maintenance, and integrates a temperature compensation algorithm to adapt to ambient temperature fluctuations: -10 Up to 50 .

[0029] The control processing unit includes: The microprocessor runs an algorithm that calculates ammonia nitrogen concentration based on absorbance data and a standard curve. The calculation formula is as follows: ; in Indicates ammonia nitrogen concentration. This indicates the absorbance measured at a wavelength of 697 nm. and The coefficients of the standard curve are determined through periodic calibration; the correlation coefficient is also mentioned. Furthermore, calibration data is stored in non-volatile memory; The data module, including a display screen, data storage device, and wireless transmitter, displays concentration values ​​in real time, stores historical data with a capacity of ≥1 year, and transmits it to the cloud platform; The adaptive calibration module automatically adjusts the detection parameters based on the ambient temperature: it obtains water quality parameters through a temperature sensor, including dynamically optimizing the standard curve coefficients, to ensure detection accuracy within ±5% error range. The adaptive calibration logic formula is as follows: ; in For the calibrated curve coefficients, This is the temperature compensation coefficient. For ambient temperature, when the temperature of the ring wall and the navel exceeds 20-30 degrees Celsius... It will activate automatically.

[0030] The system steps are as follows: This system revolves around the chemical colorimetric reaction of ammonia nitrogen in water. Ammonia nitrogen is converted into a colorimetric compound under the action of specific reagents, and the color depth is directly proportional to the concentration. By optimizing the reagent formulation and accelerating the reaction under mild conditions, the system shortens the color development time to approximately 10 minutes. Simultaneously, spectrophotometric detection captures the absorbance signal at a fixed wavelength, and the concentration is calculated using a pre-stored standard curve. The entire process emphasizes automated control, including reagent addition, temperature regulation, and data processing, to eliminate human and environmental interference and ensure the continuity and accuracy of online monitoring. Its core advantage lies in upgrading the laboratory method to a real-time system, solving the problems of reagent instability, cumbersome operation, and error accumulation in traditional technologies.

[0031] Step 1: Water Sample Collection and Pretreatment The first step of the system is to automatically collect and pre-treat the water samples to lay the foundation for subsequent testing. The sampling unit periodically extracts water samples using an automatic pump to ensure representative sample input. Pre-treatment includes physical filtration and chemical adjustment: the filtration device removes suspended particulate matter to prevent impurities from interfering with the colorimetric reaction; simultaneously, a pH adjuster dynamically adds dilute acid and alkali solutions to stabilize the pH value of the water sample within the range of 7.0-7.5 to neutralize potential ion interference. The key to this step lies in real-time monitoring and closed-loop control, adjusting the liquid addition volume through sensor feedback to ensure the water sample condition meets the testing requirements. Pre-treatment not only improves sample homogeneity but also avoids error amplification in subsequent reactions, demonstrating the system's adaptability to complex water quality environments.

[0032] Step 2: Reagent addition and reaction initiation Next, the system automatically adds the optimized formula of colorimetric reagent and oxidant, and initiates the isothermal colorimetric reaction. The reagent unit precisely measures and injects the reagents into the reaction vessel according to a preset ratio. The addition process is controlled by a precision pump to ensure minimal dosage error. Subsequently, the reaction unit is kept at 40°C. The reaction was maintained at a constant temperature for 10 minutes to allow ammonia nitrogen to be fully converted into the colorimetric compound. Temperature control employed a PID algorithm, providing rapid response and high stability, compensating for the effects of environmental fluctuations. The core of this step was the low toxicity and high efficiency of the reagents—extending reagent lifespan through specific components and reducing the use of highly toxic substances, thereby ensuring reaction speed while improving environmental friendliness and operational safety.

[0033] Step 3: Absorbance Detection and Signal Processing After the reaction is complete, the system enters the absorbance detection stage, a crucial step in concentration calculation. The spectrophotometer in the detection unit scans the water sample at a wavelength of 640 nm, capturing the absorbance value of the chromogenic compound. This process emphasizes real-time performance and accuracy: the wavelength selector is automatically calibrated to filter stray light, and the signal processing module filters and amplifies the raw data to eliminate noise interference. The detection results are immediately transmitted to the control unit, ensuring signal integrity and instant analysis. This step solves the problem of unstable color development in traditional methods. By using a fixed wavelength and rapid scanning, deviations caused by reagent degradation and changes in light are avoided, providing reliable input for subsequent concentration calculations.

[0034] Step 4: Concentration Calculation and Data Output Based on the detected absorbance values, the system calculates the ammonia nitrogen concentration and outputs the results. The control unit calls a pre-stored standard curve to convert the absorbance into a concentration value. The calculation process includes outlier identification and confidence assessment, such as distinguishing between real pollution events and transient disturbances through tiered data processing. Finally, the data module displays, stores, and transmits the results to the monitoring platform in real time, supporting water quality safety early warning. The output stage emphasizes adaptive capabilities, dynamically adjusting calibration parameters according to ambient temperature to ensure the accuracy of results under different conditions. This reflects the system's intelligent characteristics—achieving closed-loop management across the entire chain from data acquisition to decision support, improving monitoring efficiency and application value.

[0035] System integration and operational advantages: The operation of the entire monitoring system relies on the seamless integration of its various units: the sampling unit ensures sample input, the reagent and reaction unit handles chemical transformations, the detection unit performs optical measurements, and the control unit coordinates the process and outputs results. Simultaneously, the cleaning unit automatically maintains the system after each test to prevent cross-contamination. The system's advantage lies in its continuous online capability—by monitoring reagent activity, environmental parameters, and signal quality in real time, it automatically triggers a compensation mechanism to reduce error risks. This design not only improves detection accuracy but also simplifies the operation process, making ammonia nitrogen monitoring in water more efficient, environmentally friendly, and reliable, suitable for various scenarios such as wastewater treatment plants and river monitoring stations.

[0036] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0037] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for online detection of ammonia nitrogen in water, characterized in that: Includes the following steps: S1. Collect the water sample to be tested and pre-treat it to remove interference from suspended solids; S2. Add the optimized formulation of colorimetric agent and oxidant to the water sample, wherein the colorimetric agent comprises 130g sodium salicylate, 130g sodium citrate, 1.5g sodium nitrosoferricyanide and 300g deionized water; The oxidant comprises 6.4g sodium hydroxide, 2g sodium dichloroisocyanurate, and 200g deionized water; S3. Transfer the water sample after adding reagents to a constant temperature reaction device and carry out a colorimetric reaction at 37 degrees Celsius for 10 minutes. S4. After the reaction is complete, the absorbance of the water sample is measured at a wavelength of 640 nm using a spectrophotometer. S5. Based on the pre-established standard curve, calculate the ammonia nitrogen concentration in the water sample according to the absorbance. The standard curve is established by measuring the absorbance of multiple standard solutions with known ammonia nitrogen concentrations at 640 nm, and the correlation coefficient is not less than 0.9999. S6. Output ammonia nitrogen concentration data and store and transmit it to the monitoring platform in real time.

2. The method for online detection of ammonia nitrogen in water quality according to claim 1, characterized in that: The preprocessing in step S1 includes: The automatic filtration device removes particles larger than 0.45 micrometers from the water sample, and the pH value of the water sample is adjusted to the range of 7.0-7.5 in real time using a pH adjuster. The filtration device employs a multi-stage filter structure, including a pre-filter with a pore size of 5 micrometers and a final filter with a pore size of 0.45 micrometers, to enhance the removal efficiency of suspended solids. The pH adjuster is 0.1M hydrochloric acid, which is dynamically injected through a PID controller to ensure pH stability within ±0.1, thereby eliminating ion interference and improving the consistency of the colorimetric reaction.

3. The method for online detection of ammonia nitrogen in water quality according to claim 1, characterized in that: The specific preparation method of the color developer is as follows: Sodium salicylate, potassium sodium tartrate, and sodium nitrosoferricyanide were dissolved in deionized water according to their mass concentration ratio to form a mixed solution, and a stabilizer was added to extend the shelf life of the reagent. The mass concentration ratio is defined by the following formula: ； in This indicates the mass concentration of sodium salicylate. This indicates the mass concentration of potassium sodium tartrate. This indicates the mass concentration of sodium nitrosoferricyanide; The stabilizer is disodium ethylenediaminetetraacetate, added at 0.1% of the total mass of the colorimetric reagent, and after preparation at 4... Store away from light to maintain reagent activity for more than 30 days.

4. The method for online detection of ammonia nitrogen in water quality according to claim 1, characterized in that: The specific preparation method of the oxidant is as follows: Sodium hydroxide and sodium dichloroisocyanurate are dissolved in deionized water in a molar ratio to form a solution. After that, an antioxidant is added to prevent the decomposition of sodium hypochlorite. The molar ratio of sodium hydroxide to sodium dichloroisocyanurate is 2:1, and the antioxidant is ascorbic acid, with an addition amount of 0.05% of the total mass of the antioxidant. During preparation, the solution temperature is controlled at 25±2℃. The mixture was then stirred at 300 rpm for 10 minutes using a magnetic stirrer to ensure uniformity and stability, thereby avoiding detection errors caused by oxidant degradation.

5. The method for online detection of ammonia nitrogen in water quality according to claim 1, characterized in that: The constant temperature reaction device in step S3 uses a PID temperature controller with a temperature control accuracy of ±0.5 degrees Celsius. Furthermore, the reaction time is adaptively adjusted based on the turbidity of the water sample: when the turbidity sensor detects that the turbidity of the water sample is higher than 50 NTU, the reaction time is automatically extended to 12 minutes; When the turbidity is below 50 NTU, the reaction time is maintained at 10 minutes; This adjustment is achieved through an embedded algorithm, covering a turbidity measurement range of 0-100 NTU with a resolution of 1 NTU, to compensate for light scattering interference in high-turbidity water samples, ensuring sufficient color development and accurate absorbance.

6. An online ammonia nitrogen monitoring system for water quality, used to implement the online ammonia nitrogen detection method for water quality as described in any one of claims 1-5, characterized in that: include: The sampling unit automatically collects water samples and performs preprocessing. The reagent storage and addition unit includes a colorimetric reagent storage tank, an oxidant storage tank, and a precision dispensing pump, for storing and adding the colorimetric reagent and oxidant of the optimized formulation; The reaction unit, including a temperature control device and a reaction vessel, carries out a colorimetric reaction at 40 degrees Celsius; The detection unit, including a spectrophotometer and a wavelength selector, is configured to measure absorbance at a wavelength of 640 nanometers. The control and processing unit is connected to each unit, and controls the operation sequence, processes absorbance data, calculates ammonia nitrogen concentration, and outputs the results. The cleaning unit automatically cleans itself after testing to prevent cross-contamination. The cleaning solution is a 0.1% sodium hypochlorite solution, and the cleaning cycle is performed after each test.

7. The online ammonia nitrogen monitoring system for water quality according to claim 6, characterized in that: The sampling unit includes: An automatic sampling pump periodically collects water samples. The sampling frequency can be set from 1 to 60 minutes per sample, and the sampling volume is calibrated via a flow meter with an accuracy of ±0.5 mL. The pretreatment module includes a filter and a pH adjuster. The filter uses a 0.45-micron pore size membrane to remove suspended solids and is equipped with a backwashing function to extend the membrane life. The pH regulator uses dilute hydrochloric acid (0.1M) to adjust the pH of the water sample to 7.0-7.5 in real time. The pH sensor has an accuracy of ±0.05, and the data is fed back to the PLC controller to achieve closed-loop control.

8. The online ammonia nitrogen monitoring system for water quality according to claim 6, characterized in that: The reagent storage and addition unit also includes: Multiple independent reagent containers, each storing colorimetric reagent, oxidant, and cleaning solution, are made of corrosion-resistant glass, have a capacity of 1L, and are equipped with a level sensor with an accuracy of ±10mL. The dispensing pump is a precision peristaltic pump driven by a stepper motor, with a dispensing accuracy of ±0.1 mL and a flow rate range of 0.1-5 mL / s; The reagent status monitoring sensor monitors the reagent level and stability in real time, including an optical sensor to detect changes in reagent color and an audible and visual alarm to warn of reagent failure.

9. The online ammonia nitrogen monitoring system for water quality according to claim 6, characterized in that: The temperature control device for the reaction unit includes: PTC heating element, temperature sensor: accuracy ±0.1 With a PID controller, the temperature control range is 30-50 degrees Celsius, the accuracy is ±0.5 degrees Celsius, and the response time is less than 30 seconds; The reaction vessel is made of quartz, has a volume of 10 ml, and is equipped with a stirrer with an adjustable speed range of 100-500 rpm to accelerate reagent mixing; The container is designed to be detachable for easy cleaning and maintenance, and integrates a temperature compensation algorithm to adapt to ambient temperature fluctuations: -10 Up to 50 .

10. The online ammonia nitrogen monitoring system for water quality according to claim 6, characterized in that: The control processing unit includes: The microprocessor runs an algorithm that calculates ammonia nitrogen concentration based on absorbance data and a standard curve. The calculation formula is as follows: ； in Indicates ammonia nitrogen concentration. This indicates the absorbance measured at a wavelength of 697 nm. and The coefficients of the standard curve are determined through periodic calibration; the correlation coefficient is also mentioned. Furthermore, calibration data is stored in non-volatile memory; The data module, including a display screen, data storage device, and wireless transmitter, displays concentration values ​​in real time, stores historical data with a capacity of ≥1 year, and transmits it to the cloud platform; The adaptive calibration module automatically adjusts the detection parameters based on the ambient temperature by acquiring water quality parameters through a temperature sensor. This includes dynamically optimizing the standard curve coefficients to ensure that the detection accuracy is within ±5% of the error range.

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