An on-line monitoring system for nitrate nitrogen in water body and a quantitative determination method

Abstract

The present application relates to the technical field of water quality monitoring, in particular to a water body nitrate nitrogen online monitoring system and a quantitative determination method. The present application uses an online full spectrum instrument to collect water sample data, and uses a differential derivative method to realize water body nitrate nitrogen quantification. The system comprises an online area light source module, an online area spectrum acquisition module, a dilution area pure water module, a dilution area light source module, a dilution area spectrum acquisition module, a spectrum information processing module and a power module, can perform in-situ monitoring or dilution monitoring according to water body characteristics, has a wide linear range and strong generalization ability. The system and method are suitable for nitrate nitrogen online monitoring of municipal pipeline sewage, urban domestic sewage, river water, lake water and other water bodies, have high universality and low monitoring cost, and can provide strong support for real-time monitoring of water body nitrate nitrogen.

Description

Technical Field

[0001] This invention relates to the field of water quality monitoring technology, specifically to an online monitoring system for nitrate nitrogen in water and a quantitative determination method thereon. Background Technology

[0002] With economic development, people's requirements for living environment are increasing day by day. Good water quality is an important prerequisite for ensuring people's production and life. Therefore, it is necessary to monitor water quality indicators in real time.

[0003] Nitrate nitrogen is generally formed from the conversion of nitrogen-containing organic matter and is an important water quality monitoring indicator. Monitoring its concentration has different significance in different scenarios. In wastewater systems, nitrate nitrogen concentration indicates the effectiveness of nitrification and denitrification, and has important guiding value for controlling and adjusting process parameters and identifying abnormal water quality indicators. In water supply systems such as lakes and rivers, nitrate nitrogen concentration is strictly limited to below 10 mg / L. Excessive nitrate concentrations, when ingested by humans, may cause health problems and have a potential risk of inducing cancer.

[0004] Existing methods for monitoring nitrate nitrogen in water bodies mainly include the phenol disulfonic acid spectrophotometric method and ion chromatography. These methods suffer from problems such as secondary pollution, long detection times, the need for pretreatment, and expensive equipment, making them unsuitable for real-time on-site monitoring. Ultraviolet (UV) full-spectrum methods, due to their advantages of rapid sampling, non-contact operation, no pollution, and strong generalization, have been widely used in online monitoring. However, directly using the raw absorption spectrum of a UV full-spectrum instrument for online monitoring of nitrate nitrogen in different types of water bodies presents problems such as interference from organic matter and turbidity. Therefore, there is an urgent need to develop a UV full-spectrum system and method suitable for the specific monitoring of nitrate nitrogen. Summary of the Invention

[0005] The purpose of this invention is to provide an online monitoring system and quantitative determination method for nitrate nitrogen in water, so as to solve the problems existing in the real-time monitoring of nitrate nitrogen in water using ultraviolet full spectrometers.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: an online nitrate nitrogen monitoring system for water bodies, comprising an online full-spectrum instrument, wherein the online full-spectrum instrument comprises an online region light source module, an online region spectrum acquisition module, a dilution region pure water module, a dilution region light source module, a dilution region spectrum acquisition module, a spectral information processing module, and a power supply module;

[0007] The aforementioned online light source module is used to provide the light source required for online spectral acquisition;

[0008] The online area spectral acquisition module is used to acquire spectral information of water samples monitored in the online area;

[0009] The pure water module in the dilution zone is used to provide pure water for diluting water samples in the dilution zone.

[0010] The dilution zone light source module is used to provide the light source required for spectral acquisition in the dilution zone;

[0011] The dilution zone spectral acquisition module is used to acquire spectral information of the water sample monitored in the dilution zone;

[0012] The aforementioned spectral information processing module is used to process and analyze the spectral information of water samples acquired by the online area spectral acquisition module and / or the dilution area spectral acquisition module, and output the nitrate nitrogen concentration value of the water sample.

[0013] The power supply module is used to provide power to the online zone light source module, the online zone spectrum acquisition module, the dilution zone pure water module, the dilution zone light source module, the dilution zone spectrum acquisition module, and the spectral information processing module.

[0014] Furthermore, the online area light source module and the dilution area light source module include, but are not limited to, xenon lamps and deuterium lamps.

[0015] Furthermore, the power module includes, but is not limited to, wire-powered, battery-powered, and solar-powered power.

[0016] Furthermore, the water samples include, but are not limited to, municipal sewage, urban domestic sewage, river water, and lake water.

[0017] A quantitative determination method for nitrate nitrogen in water is proposed, which involves collecting water sample data using an online full-spectrum instrument and employing the differential derivative method to quantify nitrate nitrogen in water. The differential derivative method uses the first derivative, and the difference between the peak value of the first derivative of the sample and the wavelength derivative value of a nearby smooth region is compared with the difference between the peak derivative value of a unit nitrate standard water sample and the wavelength derivative value of a nearby smooth region to calculate the nitrate nitrogen concentration in the water.

[0018] Furthermore, the determination method includes a general determination procedure and a dilution determination procedure.

[0019] Furthermore, the general measurement procedure includes the following steps:

[0020] S1. The online zone light source module provides the light source, and the water sample acquires spectral data through the online zone spectral acquisition module.

[0021] S2. The online spectral acquisition module transmits the data to the spectral information processing module, which identifies that the nitrate nitrogen concentration in the water body does not exceed the linear range.

[0022] S3, the online area spectral acquisition module transmits the data to the spectral information processing module to process the water sample spectral information and predict the nitrate nitrogen concentration value of the water body.

[0023] Furthermore, the dilution determination procedure includes the following steps:

[0024] S1. The online zone light source module provides the light source, and the water sample acquires spectral data through the online zone spectral acquisition module.

[0025] S2. The online area spectral acquisition module transmits the data to the spectral information processing module. The spectral information processing module identifies the nitrate nitrogen concentration in the water body that exceeds the linear range and automatically provides the dilution factor.

[0026] S3. According to the dilution ratio, a certain amount of water sample and a certain amount of pure water enter the dilution zone spectral acquisition module through pipelines, and the light source module of the dilution zone provides light source to acquire the spectral data of the water sample in the dilution zone;

[0027] S4. The dilution zone spectral acquisition module transmits the data to the spectral information processing module to process the water sample spectral information and predict the nitrate nitrogen concentration value of the water body.

[0028] Furthermore, the linear range of nitrate nitrogen is 0.072–4 mg / L, the detection limit of nitrate nitrogen is 0.018 mg / L, and the absolute measurement error of nitrate nitrogen is ±0.1 mg / L.

[0029] Furthermore, the online full-spectrum instrument has a light source scanning wavelength range of 185–300 nm, and the peak and nearest-neighbor smooth region range used in the differential derivative method is 200–240 nm.

[0030] The beneficial effects of this invention are as follows: The system and method of this invention have strong generalizability and low monitoring cost, and can provide technical support for online quantitative monitoring of nitrate nitrogen in various types of water bodies. First, by collecting data from the full ultraviolet spectrum of water samples, the limitations of single-spectrum or dual-wavelength spectra are avoided, and the changing trends of water samples in each band are more clearly understood, resulting in richer and more comprehensive water quality information. At the same time, the introduction of the first-derivative difference spectroscopy method can effectively avoid the interference of organic matter and turbidity on nitrate nitrogen determination. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of the online full-spectrum instrument of the present invention;

[0032] Figure 2 This is a schematic diagram of the workflow of the online full-spectrum instrument of this invention;

[0033] Figure 3 The original spectral data of the entire process of a wastewater treatment plant were collected by the online full-spectrum instrument of this invention.

[0034] Figure 4 The present invention uses an online full-spectrum instrument to collect first-derivative spectra of the entire process of a wastewater treatment plant.

[0035] Figure 5 This is a regression curve of the nitrate nitrogen concentration values ​​of a wastewater treatment plant throughout the entire process, calculated by the first derivative difference spectroscopy method according to this invention, and the actual values ​​calculated by the national standard method.

[0036] The names corresponding to each mark in the diagram:

[0037] 1. Online zone spectral acquisition module; 2. Online zone light source module; 3. Spectral information processing module; 4. Power supply module; 5. Dilution zone light source module; 6. Dilution zone spectral acquisition module; 7. Dilution zone pure water module. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0039] like Figure 1-2 As shown, the online nitrate nitrogen monitoring system for water bodies according to the present invention includes:

[0040] Online area light source module 2 is used to provide the light source required for online area spectral acquisition;

[0041] Online zone spectral acquisition module 1 is used to acquire spectral information of water samples monitored in the online zone;

[0042] The pure water module 7 in the dilution zone is used to provide pure water for diluting water samples in the dilution zone.

[0043] Dilution zone light source module 5 is used to provide the light source required for spectral acquisition in the dilution zone;

[0044] The dilution zone spectral acquisition module 6 is used to acquire spectral information of the water samples monitored in the dilution zone.

[0045] The spectral information processing module 3 is used to process and analyze the spectral information of the water sample acquired by the online area spectral acquisition module 1 or the dilution area spectral acquisition module 6, and output the nitrate nitrogen concentration value of the water sample.

[0046] Power module 4 is used to provide power to online zone light source module 2, online zone spectrum acquisition module 1, dilution zone light source module 5, dilution zone spectrum acquisition module 6, spectral information processing module 3, and dilution zone pure water module 7.

[0047] The principle of this invention is as follows:

[0048] This invention proposes an online monitoring system and quantitative determination method for nitrate nitrogen in water bodies based on the ultraviolet full-spectrum derivative method, considering two factors. Firstly, existing methods suffer from problems such as secondary pollution, long detection times, the need for pretreatment, and expensive equipment, making them unsuitable for real-time on-site monitoring. Secondly, directly using the raw absorption spectrum of an ultraviolet full-spectrum instrument for online monitoring of nitrate nitrogen in different types of water bodies presents problems such as interference from organic matter and turbidity.

[0049] A quantitative determination procedure based on the ultraviolet full-spectrum derivative method was constructed for the online monitoring system of nitrate nitrogen in water bodies. It consists of two parts: a general determination procedure and a dilution determination procedure, including:

[0050] In a typical measurement process, when the nitrate nitrogen concentration in the water sample is within the linear range, the online light source module 2 provides a light source, and the water sample acquires spectral data through the online spectral acquisition module 1. The online spectral acquisition module 1 transmits the data to the spectral information processing module 3 to process the spectral information of the water sample and predict the nitrate nitrogen concentration value of the water body.

[0051] The dilution measurement process involves an online light source module 2 providing the light source. Water samples are sampled and their spectral data is acquired by an online spectral acquisition module 1. This data is then transmitted to a spectral information processing module 3, which identifies instances where the nitrate nitrogen concentration exceeds the linear range and automatically assigns the dilution factor. Based on this dilution factor, a fixed quantity of water sample and a fixed quantity of pure water are piped into a dilution zone spectral acquisition module 6. Here, a light source module 5 provides the light source to acquire the water sample's spectral data. The dilution zone spectral acquisition module 6 transmits this data to the spectral information processing module 3, which processes the spectral information and predicts the nitrate nitrogen concentration in the water.

[0052] This invention uses an online full-spectrum analyzer to collect water sample data and employs the differential derivative method to quantify nitrate levels in water. The online full-spectrum analyzer has a light source scanning wavelength range of 185–300 nm, enabling continuous, high-frequency online monitoring with a single scan time not exceeding six seconds. The light source used includes, but is not limited to, xenon lamps and deuterium lamps; energy sources include, but are not limited to, wire power, battery power, and solar power. The differential derivative method uses the first derivative. The nitrate nitrogen concentration in the water is calculated by comparing the difference between the peak derivative value of the sample's first derivative and the derivative value of a certain wavelength in the nearest smooth region with the difference between the peak derivative value of a unit nitrate standard water sample and the derivative value of a certain wavelength in the nearest smooth region. The peak and nearest smooth region range used is 200–240 nm. The method and system of this invention are applicable to water bodies including, but not limited to, municipal sewage, urban domestic sewage, river water, and lake water. The detection limit for nitrate nitrogen measured by the method and system is 0.018 mg / L, the linear range is 0.072–4 mg / L, and the absolute measurement error is ±0.1 mg / L.

[0053] Example 1

[0054] Taking a wastewater treatment plant's entire process water sample as an example, when the water sample passes through an online full-spectrum analyzer, the online region spectral acquisition module 1 collects spectral data and transmits it to the spectral information processing module 3 to process the water sample's spectral information. The spectral information processing module 3 performs a first-order derivative on the collected water sample, such as... Figure 3-4 As shown, the nitrate nitrogen-containing water sample has a significant peak at 216 nm. In the nearby smooth region, 230 nm is selected as the differential wavelength. The first derivative of the absorbance of the water sample at 216 nm is subtracted from the first derivative of the absorbance at 230 nm. This difference is then compared with the difference in the first derivatives of the standard nitrate nitrogen water sample at 216 nm and 230 nm for a unit concentration to obtain the predicted nitrate nitrogen value. If the predicted value is within the linear range, the nitrate nitrogen concentration determination is considered complete.

[0055] If the predicted value is outside the linear range, divide the predicted value by two. If the resulting value is within the linear range, determine the dilution factor as two times; otherwise, continue dividing by two until the resulting value is within the linear range.

[0056] After determining the dilution factor, a fixed amount of water sample and a fixed amount of pure water are piped into the dilution zone spectral acquisition module 6. The dilution zone light source module 5 provides a light source to acquire the spectral data of the water sample. The dilution zone spectral acquisition module 6 transmits the data to the spectral information processing module 3 to process the spectral information of the water sample. The spectral information processing module 3 performs first derivative on the spectrum of the diluted water sample, subtracts the value of the derivative spectrum at 216nm from the value at 230nm, and compares it with the difference of the first derivative of the standard nitrate nitrogen water sample at 216nm and 230nm for a unit concentration to obtain the predicted value of nitrate nitrogen in the diluted water sample. Finally, the predicted value is multiplied by the dilution factor to obtain the predicted value of nitrate nitrogen in the water sample to be tested.

[0057] like Figure 5 As shown, the regression curve of the nitrate nitrogen concentration value of the entire process water sample of a wastewater treatment plant, predicted after spectral acquisition and processing, and the actual value according to the national standard method, has a correlation coefficient of 0.999, indicating a good linear relationship.

[0058] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes in shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. An online monitoring system for nitrate nitrogen in water, characterized in that: The system includes an online full-spectrum instrument, which comprises an online region light source module (2), an online region spectrum acquisition module (1), a dilution region pure water module (7), a dilution region light source module (5), a dilution region spectrum acquisition module (6), a spectrum information processing module (3), and a power supply module (4). The online area light source module (2) is used to provide the light source required for online area spectral acquisition; The online area spectral acquisition module (1) is used to acquire the spectral information of the water sample monitored in the online area; The pure water module (7) in the dilution zone is used to provide pure water for diluting water samples in the dilution zone; The dilution zone light source module (5) is used to provide the light source required for spectral acquisition in the dilution zone; The dilution zone spectral acquisition module (6) is used to acquire the spectral information of the water sample monitored in the dilution zone; The spectral information processing module (3) is used to process and analyze the spectral information of the water sample collected by the online area spectral acquisition module (1) and / or the dilution area spectral acquisition module (6), and output the nitrate nitrogen concentration value of the water sample. The power supply module (4) is used to provide power to the online area light source module (2), the online area spectrum acquisition module (1), the dilution area pure water module (7), the dilution area light source module (5), the dilution area spectrum acquisition module (6), and the spectrum information processing module (3); The water samples include municipal sewage, river water, or lake water. The determination method of the water body nitrate nitrogen online monitoring system includes a general determination procedure and a dilution determination procedure; The general measurement procedure includes the following steps: S11, the online zone light source module (2) provides the light source, and the water sample collects spectral data through the online zone spectral acquisition module (1); S12, the online area spectral acquisition module (1) transmits the data to the spectral information processing module (3), and the spectral information processing module (3) identifies that the nitrate nitrogen concentration in the water body does not exceed the linear range; S13. The online area spectral acquisition module (1) transmits the data to the spectral information processing module (3) to process the spectral information of the water sample and predict the nitrate nitrogen concentration value of the water body; The dilution measurement procedure includes the following steps: S21. The online zone light source module (2) provides the light source, and the water sample acquires spectral data through the online zone spectral acquisition module (1); S22. The online area spectral acquisition module (1) transmits the data to the spectral information processing module (3). The spectral information processing module (3) identifies the superlinear range of nitrate nitrogen concentration in the water body and automatically provides the dilution factor. S23. According to the dilution ratio, a certain amount of water sample and a certain amount of pure water enter the dilution zone spectral acquisition module (6) through the pipeline, and the light source module (5) of the dilution zone provides the light source to acquire the spectral data of the water sample in the dilution zone; S24. The dilution zone spectral acquisition module (6) transmits the data to the spectral information processing module (3) to process the water sample spectral information and predict the nitrate nitrogen concentration value of the water body. Water sample data were collected using an online full-spectrum instrument, and the nitrate nitrogen concentration in the water was quantified using the differential derivative method. The differential derivative method uses the first derivative, and the difference between the peak value of the first derivative of the sample and the wavelength value of the derivative in the nearest smooth region is compared with the difference between the peak value of the first derivative of the water sample of a unit nitrate standard and the wavelength value of the derivative in the nearest smooth region to calculate the nitrate nitrogen concentration in the water. The online full-spectrum instrument has a light source scanning wavelength range of 185~300nm, and the peak and nearest-neighbor smooth region range used in the differential derivative method is 200~240nm.

2. The online monitoring system for nitrate nitrogen in water according to claim 1, characterized in that: The online zone light source module (2) and the dilution zone light source module (5) include xenon lamps or deuterium lamps.

3. The online monitoring system for nitrate nitrogen in water according to claim 1, characterized in that: The power module (4) includes wire power supply, battery power supply or solar power supply.

4. The online monitoring system for nitrate nitrogen in water according to claim 1, characterized in that: The linear range of nitrate nitrogen is 0.072~4 mg / L, the detection limit of nitrate nitrogen is 0.018 mg / L, and the absolute measurement error of nitrate nitrogen is ±0.1 mg / L.

Images