CN106596436B - Multi-parameter water quality real-time online monitoring device based on spectrum method - Google Patents

Abstract

The invention relates to a multi-parameter water quality real-time online monitoring device based on a spectrum method. The device comprises a hernia lamp light source, a preposed light path, a spectrum acquisition unit, a rapid processing platform and an output unit; emergent light of the hernia lamp light source is divided into a correction reference light path and a measurement light path after passing through a front light path; the calibration reference light path is incident to the spectrum acquisition unit through a water sample to be detected; the measuring light path is incident to the spectrum acquisition unit through the standard water sample; the calibration reference light path and the measurement light path are synchronously acquired by the spectrum acquisition unit and then converted into two groups of spectrum curve digital signals to be sent to the fast processing unit; the rapid processing unit respectively processes the two sets of spectral curve digital signals to obtain the substances to be detected in the water sample to be detected and the concentration of the substances to be detected, and then the substances to be detected are output to the local or remote through the output unit to realize monitoring. The device has short test period, small volume and low cost and can realize real-time multi-parameter water quality measurement.

Description

A multi-parameter real-time online water quality monitoring device based on spectroscopy

Technical Field

The invention belongs to the technical field of optical detection, and in particular relates to a multi-parameter real-time online water quality monitoring device based on spectroscopy.

Background Art

Water resource pollution is one of the most serious problems facing the world's water environment today. How to timely, accurately, quickly and comprehensively reflect the status of water environment quality and pollution sources is the premise and basis for formulating practical pollution prevention and control plans and pollution source status.

At present, there are several methods based on water quality detection: chemical analysis, atomic or molecular spectroscopy, chromatographic separation technology, electrochemical analysis technology, and biosensor technology;

Among them, water quality analyzers based on chemical methods have problems such as long sampling and testing cycle, single parameter measurement, secondary pollution, time-consuming and labor-intensive in water quality monitoring;

Water quality analyzers based on atomic or molecular spectroscopy and chromatographic separation have problems such as inability to analyze multiple parameters simultaneously, narrow linear range of standard working curves, and low accuracy when analyzing complex samples during water quality monitoring.

Although water quality analyzers based on electrochemical analysis technology are portable, they have problems such as pollution, energy consumption, and high processing costs when monitoring water quality.

Biosensor technology may cause irreversible chemical reactions between the recognition element and the substance to be tested, which will affect the recognition ability and sensitivity. In addition, miniaturization is difficult to achieve.

Summary of the invention

In order to solve the problems in the background technology, the present invention provides a multi-parameter real-time online water quality monitoring device based on spectroscopy, which has a short test cycle, a small size, a low cost and can realize real-time, multi-parameter water quality measurement.

The basic principle of the present invention is:

The multi-parameter real-time online water quality monitoring device based on spectroscopy is a method that uses the absorption spectrum curves of polluting elements in water at different wavelengths to determine the composition and content of polluting elements. According to the Lambert-Beer law, the composition of pollutants is determined by the position of the "peak" and "valley" of the polluting element spectrum curve, and the concentration of the polluting element is determined by its amplitude combined with the calibration method, thereby achieving qualitative and quantitative detection of multiple water quality parameters. The raw data of water body measurement is unmixed and reconstructed in real time based on the high-speed ARM processing unit, and then provided to the user unit in various forms such as wireless, wired, and solid-state storage.

The device can monitor the properties and contents of various substances in water, including chromaticity, turbidity, chemical oxygen demand (COD), biochemical oxygen demand (BOD), total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), nitrate, cyanide ion, hexavalent chromium, bromide ion (Br-, bromide), colored dissolved organic matter (CDOM), etc.

The specific technical solution of the present invention is:

The present invention provides a multi-parameter real-time online water quality monitoring device based on spectroscopy, which is characterized by comprising a xenon lamp source, a front optical path, a spectrum acquisition unit, a rapid processing platform and an output unit;

The light emitted by the xenon lamp source is divided into a correction reference light path and a measurement light path after passing through the front light path; the correction reference light path is incident on the spectrum acquisition unit through the water sample to be tested; the measurement light path is incident on the spectrum acquisition unit through the standard water sample; the correction reference light path and the measurement light path are synchronously acquired by the spectrum acquisition unit and converted into two sets of spectrum curve digital signals and then sent to the fast processing unit; the fast processing unit processes the two sets of spectrum curve digital signals respectively to obtain the substances to be tested and the concentrations of the substances to be tested in the water sample to be tested, and then outputs them to the local or remote through the output unit to achieve monitoring;

The rapid processing unit is an ARM-based multi-parameter intelligent water quality processing platform.

The spectrum acquisition unit includes a first collimator, a slit, a first reflector, an optical fiber bundle, a grating, a second collimator, a detector, and a second reflector;

After passing through the standard water sample, the correction reference light path passes through the second collimator, is transmitted to the slit through the optical fiber bundle at the primary image plane position of the second collimator, and then is reflected to the grating through the first reflector. The grating disperses the correction reference light path, and then is reflected by the second reflector and received by the detector;

After passing through the water sample to be measured, the measuring light path passes through the first collimator, passes through the optical fiber bundle to the slit at the primary image plane position of the first collimator, and then is reflected to the grating by the first reflector. The grating disperses the light path of the water sample to be measured, and then is reflected by the second reflector and received by the detector.

The spectrum of the output light emitted by the xenon lamp source module includes ultraviolet light, visible light, and near-infrared light, and the spectrum range is 185nm to 1100nm.

The grating is a plane grating, a concave grating, a concave holographic grating or an adjustable blazed grating.

The detector is a silicon photoelectric tube or an array detector.

The output unit is a network transmission line, wireless transmission or solid-state storage.

Specifically, the front optical path includes an imaging mirror and a collimating mirror.

The fast processing unit in the present invention processes two groups of spectrum curve digital signals respectively, and the specific processing process includes the following steps:

1) Establish a standard database; the standard sample database includes different substances dissolved in water, characteristic spectra of different substances, and the material composition is determined by the "reflection peak" or "absorption valley" of the characteristic spectrum; the concentration of the substance is determined by the amplitude value corresponding to the characteristic spectrum position of each material component;

2) Determination of substances in the water sample to be tested;

2.1) Obtaining a characteristic spectrum A of the standard water sample through the digital signal of the spectrum curve of the standard water sample;

2.2) Obtaining a characteristic spectrum B of the water sample to be tested through the spectrum curve digital signal of the water sample to be tested;

2.3) The characteristic spectrum A of the standard water sample and the characteristic spectrum B of the water sample to be tested are normalized and subtracted to obtain the "reflection peak" or "absorption valley" of the characteristic spectrum C, and the standard database is searched to determine the material composition of the water sample to be tested. If the water sample to be tested contains only a single substance, proceed to step 3); if the water sample to be tested contains multiple substances, proceed to step 4);

3) Concentration detection of a single substance in the water sample to be tested:

3.1) Calculate the coefficient matrix K based on the sample database and absorbance formula as follows:

Where: I ₁ , I ₂ , ...I _n are the amplitude values of the known continuous spectrum after the measuring light path passes through the water sample to be tested for multiple times in the standard database, I _0-1 , I _0-2 , I _0-n are the known continuous spectrum amplitude values of the calibration reference light path in the standard database after passing through the standard water sample, C ₁ , C ₂ , ...C _n are the component concentrations at each absorbance, and L is the fixed optical path difference;

3.2) Then, according to the absorbance formula of Lambert-Beer's law, calculate the concentration measured after the calibration reference light path passes through the water sample for the i-th time:

Where: I _i is the amplitude value of the continuous spectrum obtained after passing through the water sample to be tested, I _0-i is the amplitude value of the continuous spectrum after passing through the standard water sample, _Ci is the concentration of a single substance in the water sample to be tested, L is a fixed optical path difference, and the concentration of the substance in the sample to be tested can be obtained by substituting the obtained K value, as shown in the following formula:

4) Concentration detection of multiple substances in the water sample to be tested:

4.1) Calculate the coefficient matrix K based on the sample database and absorbance formula as follows:

Where: I ₁ , I ₂ , ...I _n are the amplitude values of the continuous spectrum known after the measurement light path in the database passes through the water sample to be tested for multiple times, I _0-1 , I _0-2 , I _0-n are the amplitude values of the continuous spectrum after the correction reference light path in the database passes through the standard water sample, C _nm is the nth concentration of the mth substance, and L is the fixed optical path difference;

4.2) Then, according to the absorbance formula of Lambert-Beer's law, calculate the concentration measured after the calibration reference light path passes through the water sample for the i-th time:

I _i is the amplitude value after passing through the water sample to be tested, I _0-i is the intensity value after passing through the standard water sample, C _i is the i-th component and its concentration, L is the fixed optical path difference, and the concentration to be tested can be obtained by substituting the obtained K value, as shown in the following formula:

Then C ₁ , C ₂ , ...C _i , C _n are the concentrations of various substances in the corresponding water samples to be tested.

The advantages of the present invention are:

1. The existing chemical method for water quality measurement can only measure the composition and concentration of a single water quality element.

It has the ability to obtain multi-parameter water quality components and concentrations.

2. The existing optical water quality measurement does not have a reference correction design for synchronous measurement. The present invention designs a dual-beam reference optical path for synchronous measurement, which has the ability to actively correct system errors. The accuracy of long-term measurement is very high, especially for the correction of light intensity attenuation caused by long-term use of xenon lamps.

3. The present invention uses a concave holographic grating or an adjustable blazed grating. Compared with the traditional method, it can achieve a high signal-to-noise ratio and measurement accuracy while miniaturizing the prototype.

4. The instrument corresponding to the present invention is small in size, light in weight, does not require reagents or pre-sampling, is plug-and-play, and has a fast response.

5. The present invention does not require the addition of any chemical solution for measurement and will not cause secondary pollution of the water body, which has significant advantages over traditional chemical methods.

6. The present invention has the ability to process and analyze multiple parameters of water quality in real time online and can be networked for detection. It has obvious advantages over traditional detection methods such as single probes and non-real-time measurements.

7. The present invention adopts multiple interfaces for flexible output, which has significant advantages over the traditional single interface and manual reading.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the optical structure of the present invention.

The reference numerals are as follows:

1-xenon lamp light source, 2-front optical path, 3-first collimator, 4-slit, 5-first reflector, 6-optical fiber bundle, 7-grating, 8-second collimator, 9-detector, 10-second reflector, 11-fast processing platform, 12-output unit.

DETAILED DESCRIPTION

As shown in Figure 1, the multi-parameter real-time online monitoring device for water quality based on optical spectroscopy provided by the present invention includes a xenon lamp light source 1, 2, a front light path 2, a first collimator 3, a slit 4, a first reflector 5, an optical fiber bundle 6, a grating 7, a second collimator 8, a detector 9, a second reflector 10, a rapid processing platform 11, and an output unit 12.

The specific implementation of the present invention is as follows:

The light emitted by the xenon lamp light source 1 (the spectrum of the xenon lamp light source covers: ultraviolet light, visible light, near-infrared light, and the spectrum range is 185nm~1100nm) passes through the front optical path 2 and is divided into two beams. The first beam of light (this beam of light is the calibration reference optical path) passes through the standard water sample, and the second beam of light (this beam of light is the measurement optical path) passes through the water sample to be measured. Among them, after the first beam passes through the second collimator 8, the optical signal is transmitted to the slit 4 through the optical fiber bundle 6 at the primary image plane of the second collimator 8, and then enters the first reflector 5 and passes through the dispersion of the grating 7 (the grating can select different gratings such as plane grating, concave grating, concave holographic grating, adjustable blazed grating, etc.) and then is reflected by the second reflector 10 to the detector 9 (the detector can select silicon phototube, area array detector).

After the second light beam passes through the first collimator 3, the optical signal is transmitted to the slit 4 through the optical fiber bundle 6 at the primary image plane of the first collimator 3, and is incident on the first reflector 5. After being reflected by the first reflector 5, it is dispersed by the grating 7, and then passes through the second reflector 10 to the detector 9. After the two light beams are dispersed, they are distributed on different rows of pixels of the detector. After photoelectric conversion, the obtained spectral information digital signal is transmitted to the fast processing platform 11 (ARM-based water quality multi-parameter intelligent processing platform). The fast processing platform 11 performs dark current removal, filtering, spectral data extraction, water quality multi-parameter spectral unmixing and other processing on the electrical signals converted from the two light beams to obtain the substances to be tested and the concentrations of the substances to be tested in the water sample to be tested, and sends them to the local or remote through the output unit 12 to realize monitoring; the output unit includes various forms of network transmission lines, wired methods, antennas, solid-state storage, etc.

Among them, the ARM-based multi-parameter intelligent water quality processing platform is a circuit board card based on the ARM chip processor. On this chip device, Linux and Android systems can be loaded for algorithm processing.

The specific algorithm processing includes the following steps:

The fast processing unit processes the two sets of spectrum curve digital signals respectively, including the following steps:

Step 1) Establishing a standard database; the standard sample database includes different substances dissolved in water, characteristic spectra of different substances, and determining the substance composition through the "reflection peak" or "absorption valley" of the characteristic spectrum; determining the concentration of the substance through the amplitude value corresponding to the characteristic spectrum position of each substance component;

Step 2) determination of substances in the water sample to be tested;

Step 2.1) obtaining a characteristic spectrum A of the standard water sample through a digital signal of a spectrum curve of the standard water sample;

Step 2.2) obtaining a characteristic spectrum B of the water sample to be tested through the spectrum curve digital signal of the water sample to be tested;

Step 2.3) The characteristic spectrum A of the standard water sample and the characteristic spectrum B of the water sample to be tested are normalized and subtracted to obtain the "reflection peak" or "absorption valley" of the characteristic spectrum C, and the standard database is searched to determine the material composition of the water sample to be tested. If the water sample to be tested contains only a single substance, proceed to step 3); if; if the water sample to be tested contains multiple substances, proceed to step 4);

Step 3) Concentration detection of a single substance in the water sample to be tested:

Step 3.1) Calculate the coefficient matrix K based on the sample database and absorbance formula as follows:

Where: I ₁ , I ₂ , ...I _n are the amplitude values of the continuous spectrum after the measurement light path in the standard database passes through the water sample to be tested for multiple times, I _0-1 , I _0-2 , I _0-n are the amplitude values of the continuous spectrum after the correction reference light path in the standard database passes through the standard water sample, C ₁ , C ₂ , ...C _n are the component concentrations at each absorbance, and L is the fixed optical path difference;

Step 3.2) Calculate the concentration measured after the calibration reference light path passes through the water sample for the i-th time based on the absorbance formula of the Lambert-Beer law:

Where: I _i is the amplitude value obtained after passing through the water sample to be tested, I _0-i is the amplitude value obtained after passing through the standard water sample, _Ci is the component concentration, L is the fixed optical path difference, and the concentration of the substance in the sample to be tested can be obtained by substituting the obtained K value, as shown in the following formula:

Step 4) Concentration detection of multiple substances in the water sample to be tested:

Step 4.1) Calculate the coefficient matrix K based on the sample database and absorbance formula as follows:

Where: I ₁ , I ₂ , …I _n are the amplitude values of the continuous spectrum after the measurement light path in the standard database passes through the water sample to be tested for multiple times, I _0-1 , I _0-2 , I _0-n are the amplitude values of the continuous spectrum after the correction reference light path in the standard database passes through the standard water sample, C _nm is the nth concentration of the mth substance, and L is the fixed optical path difference;

Step 4.2) Calculate the concentration measured after the calibration reference light path passes through the water sample for the i-th time based on the absorbance formula of the Lambert-Beer law:

I _i is the amplitude value obtained after passing through the water sample to be tested, I _0-i is the amplitude value obtained after passing through the standard water sample, C _i is the i-th component and its concentration, L is the fixed optical path difference, and the concentration to be tested can be obtained by substituting the obtained K value, as shown in the following formula:

Then C ₁ , C ₂ , ...C _i , C _n are the concentrations of the corresponding components respectively.

One point that needs to be supplemented is that the standard water sample is pure or clean and transparent water that does not contain the substance to be tested.

Claims (6)

1. A multi-parameter water quality real-time on-line monitoring device based on a spectrum method is characterized in that: the system comprises a hernia lamp light source, a preposed light path, a spectrum acquisition unit, a rapid processing platform and an output unit;

emergent light of the hernia lamp light source passes through the preposed light path and then is divided into a correction reference light path and a measurement light path; the calibration reference light path is incident to the spectrum acquisition unit through a water sample to be detected; the measuring light path is incident to the spectrum acquisition unit through the standard water sample; the calibration reference light path and the measurement light path are synchronously acquired by the spectrum acquisition unit and then converted into two groups of spectrum curve digital signals to be sent to the fast processing unit; the rapid processing unit respectively processes the two groups of spectral curve digital signals to obtain the substances to be detected in the water sample to be detected and the concentration of the substances to be detected, and then the substances to be detected are output to the local or remote through the output unit so as to realize monitoring;

the rapid processing unit is an ARM-based water quality multi-parameter intelligent processing platform;

the spectrum acquisition unit comprises a first collimating mirror, a slit, a first reflecting mirror, an optical fiber beam, a grating, a second collimating mirror, a detector and a second reflecting mirror;

after passing through a standard water sample, the correction reference light path passes through a second collimating mirror, is transmitted to the slit at the primary image surface position of the second collimating mirror through an optical fiber bundle, and is reflected to the grating through a first reflector, and the grating disperses the correction reference light path, and is reflected by a second reflector and received by a detector;

after passing through a water sample to be measured, a measuring light path passes through a first collimating mirror, passes through an optical fiber bundle to a slit at a primary image surface position of the first collimating mirror, and is reflected to a grating through a first reflector, and the grating disperses the light path of the water sample to be measured, then is reflected through a second reflector and is received by a detector;

the rapid processing unit respectively processes the two groups of spectrum curve digital signals which are synchronously acquired, and the rapid processing unit comprises the following steps:

1) Establishing a standard database; the standard sample database comprises different substances dissolved in water and characteristic spectra of the different substances, and the composition of the substances is determined through reflection peaks or absorption valleys of the characteristic spectra; determining the concentration of the substance according to the amplitude value of each substance component corresponding to the characteristic spectrum position;

2) Determining substances in a water sample to be detected;

2.1 Obtaining a characteristic spectrum A of the standard water sample through a spectrum curve digital signal of the standard water sample;

2.2 Obtaining a characteristic spectrum B of the water sample to be detected through the digital signal of the spectral curve of the water sample to be detected;

2.3 The characteristic spectrum A of the standard water sample and the characteristic spectrum B of the water sample to be detected are normalized and differentiated to obtain a 'reflection peak' or an 'absorption valley' of the characteristic spectrum C, a standard database is searched, the material components of the water sample to be detected are judged, and if the water sample to be detected only contains a single material, the step 3) is carried out; if the water sample to be detected contains various substances, performing the step 4);

3) And (3) detecting the concentration of a single substance in the water sample to be detected:

3.1 ) calculating a coefficient matrix K according to the sample database and the absorbance formula, as follows:

in the formula: i is ₁ 、I ₂ 、…I _n For measuring the known continuous spectrum amplitude value after the light path passes through the water sample to be measured for multiple times in the standard database _0-1 、I _0-2 、I _0-n For correcting known continuous spectrum amplitude value C after reference light path passes through standard water sample for multiple times in standard database ₁ 、C ₂ 、…C _n For each absorbance component concentration, L is the fixed optical path difference;

3.2 According to an absorbance formula of Lambert-beer's law, calculating the concentration measured after the ith time of the correction reference light path passing through the water sample to be detected:

in the formula: i is _i Is a continuous spectrum amplitude value obtained after passing through a water sample to be measured, I _0-i For passing through standard water samplesAcquired continuous spectral amplitude value, C _i The concentration of a single substance in a water sample to be detected is obtained by substituting the fixed optical path difference into the obtained K value, and the concentration of the substance in the sample to be detected is shown as the following formula:

4) Detecting the concentration of various substances in a water sample to be detected:

4.1 ) calculating a coefficient matrix K according to the sample database and the absorbance formula, as follows:

in the formula: i is ₁ 、I ₂ 、…I _n For measuring the known continuous spectrum amplitude value after the light path passes through the water sample to be measured for multiple times in the standard database, I _0-1 、I _0-2 、I _0-n For correcting known continuous spectrum amplitude value C after reference light path passes through standard water sample for multiple times in standard database _nm Is the nth concentration of the mth substance, and L is a fixed optical path difference;

4.2 According to an absorbance formula of Lambert-beer's law, calculating the concentration measured after the ith time of the correction reference light path passing through the water sample to be detected:

I _i is the amplitude value of the continuous spectrum after passing through the water sample to be measured, I _0-i Is the amplitude value of the continuous spectrum after passing through the standard water sample, C _i The component I and the concentration thereof, L is a fixed optical path difference, and the concentration to be measured can be obtained by substituting the obtained K value, as shown in the following formula:

then C is ₁ 、C ₂ 、…C _i 、C _n The concentrations of various substances in the corresponding water sample to be detected are respectively.

2. The multi-parameter water quality real-time on-line monitoring device based on spectroscopy as claimed in claim 1, wherein: the spectrum band of emergent light emitted by the hernia lamp light source module comprises ultraviolet light, visible light and near infrared light, and the spectrum band is 185-1100 nm.

3. The multi-parameter water quality real-time on-line monitoring device based on spectroscopy as claimed in claim 2, wherein: the grating is a plane grating, a concave holographic grating or an adjustable blazed grating.

4. The multi-parameter water quality real-time on-line monitoring device based on spectroscopy as claimed in claim 3, wherein: the detector is a silicon photoelectric tube or an area array detector.

5. The multi-parameter water quality real-time on-line monitoring device based on spectroscopy as claimed in claim 4, wherein: the output unit is a network transmission line, wireless transmission or solid state storage.

6. The multi-parameter water quality real-time on-line monitoring device based on spectroscopy as claimed in claim 5, wherein: the front light path comprises an imaging mirror and a collimating mirror.

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