CN1677087A - Device and method for water quality monitoring - Google Patents

Abstract

The invention discloses a new water quality monitor device and its technique. It comprises a optic probe with two light source of two determined wave length and signal input output optic fiber, and a semiconductor light wave length probe. The optic probe is put in the water and or in the water tube. The two light rays of different wave length goes into the probe through light coupling device, passing through the monitoring water, then the penetrating light is lead out to the optic probe single output optic fiber and surveyed by the semiconductor light wave length probe. Above water quality survey device and the technique is adaptive to remote real-time auto water quality and chroma, turbidity survey. It has water flow, weather or other factor resistance, and low energy consuming, easy operation and handily amendment, simple structure and low cost.

Description

Device and method for water quality monitoring

1. Technical field

The invention relates to a water quality monitoring device and method, in particular to a sensor technology and method suitable for remote real-time automatic monitoring of the chromaticity of sewage and natural water, and belongs to the technical field of environmental monitoring.

2. Background technology

An urgent problem facing water pollution prevention and control is how to automatically monitor in real time whether the wastewater of the sewage discharge enterprises meets the standard discharge, and conduct timely automatic monitoring and alarm for the incidents of excessive discharge of wastewater and sudden pollution of water resources, so that the environmental protection supervision department can control water according to law , Timely control and eliminate the consequences of accidents. The reason for this is that some polluting enterprises, out of consideration of their own economic interests, or have a weak sense of responsibility, spend huge sums of money to install wastewater treatment equipment, but always intentionally or unintentionally do not put it into normal operation, and the pollution control equipment has become a fraud. And the perfunctory decoration of the environmental supervision department. In addition, sudden accidents of water resources pollution also occur from time to time. The environmental monitoring department does not lack water quality testing equipment and means, what is lacking is unattended, on-site water quality, especially real-time automatic monitoring and alarm technology for running water quality. This technology requires not necessarily many parameters to be monitored, and the accuracy is not necessarily high, but it is required to be able to automatically judge whether the water quality (such as water color, turbidity, PH value or COD value) has abnormal changes, and the equipment is running It is easy to maintain, strong resistance to running water, weather or other on-site factors, and low cost. Once it detects abnormal changes in water quality, it can automatically call the police, which is convenient for environmental protection supervisors to go to the scene in time to obtain evidence and test, and to stop and punish illegal discharge behaviors according to law, or to control the spread of accident consequences.

Clean and pure natural water is colorless and transparent. In other words, colored or turbid water is polluted or not up to standard. Organic matter pollution accounts for a large proportion of all water pollution. Almost all organic matter has its own absorption characteristics in the 215-316nm area. The total organic matter content can be tested by using the ultraviolet absorption photometer. Therefore, chromaticity, turbidity and COD (chemical oxygen demand) value are important indicators for water quality monitoring. The existing methods for detecting water quality chromaticity and turbidity mainly include visual colorimetry and spectrophotometry (including spectrometry and ultraviolet absorption photometry). The former is simple and intuitive, but has large errors and is not suitable for automatic measurement; the latter can be used for quantitative and accurate measurement, and there are many parameters for measuring water quality. It can detect comprehensive indicators of pollutants and special water quality indicators. It has stable performance and has been widely used. In online detection of water quality (see Wang An, Xie Yu, Liang Zhu, "Research on Chromaticity Measurement in Water", China Environmental Monitoring, Vol. 16, No. 2, 2000, p. 37). However, the existing spectrophotometric method is not suitable for real-time automatic monitoring of remote water quality, and is not suitable for monitoring the quality of running water. It is easily affected by weather and on-site environment, and the equipment is relatively expensive. In addition, there was a report of a liquid color sensitive sensor based on the combination of colored optical glass filter and silicon photocell (see Chen Jiasheng, Ji Xinyuan, "Design of liquid color sensor using optical fiber transmission", Sensor Technology, 21st, 2002 Volume No. 9, page 21; Chen Jiasheng, "A liquid color measurement device using optical fiber transmission", utility model patent, ZL 02220059.2). It uses pulsed xenon lamp illumination, optical fiber bundle light transmission and photoelectric integration method for measurement. Since the luminescence of the pulsed xenon lamp is unstable, it is necessary to monitor the luminous intensity of the pulsed xenon lamp. Therefore, the color sensitive sensor adopts a dual optical path structure. One of the light paths is the measurement light path, and the other light path is the monitoring light path (see Chen Jiasheng, Ji Xinyuan, "Design of a liquid color sensor using optical fiber conduction", Sensor Technology, Volume 21, No. 9, 2002, page 21; Chen Jiasheng, " Liquid color measurement device using optical fiber conduction" utility model patent, ZL 02220059.2). This kind of sensor can measure chromaticity more accurately and can carry out on-site automatic measurement, but the color-sensitive sensor used needs three photocells covered with optical filters, the optical path of the measurement system is more complicated, the light source consumes a lot of power, and it is resistant to liquid disturbance and others. The ability to interfere with on-site factors is poor, and there are many difficulties in real-time automatic monitoring and alarming of sewage or natural water (especially running water) water quality in an unattended site.

3. Contents of the invention

(1) Purpose of the invention

Provided are a device and method for monitoring water quality. It can monitor changes in water quality chromaticity (including ultraviolet absorbance) and turbidity, and is suitable for remote real-time automatic monitoring and alarming of abnormal water quality changes caused by heavy metals, dyes and organic matter pollution.

(2) Technical solution

A device for monitoring water quality is characterized in that it includes a light source with two specific peak wavelengths, an optical probe with signal input and output optical fibers, and a semiconductor light wavelength detector capable of measuring the central wavelength of quasi-monochromatic light. The light of two specific peak wavelengths emitted by the light source enters the optical probe through the signal input optical fiber. After passing through the water to be monitored, the optical signal is drawn out from the output optical fiber of the optical probe and detected by the semiconductor optical wavelength detector.

The two light sources with specific peak wavelengths can be two semiconductor light-emitting diodes, two semiconductor laser diodes or an ultraviolet lamp plus two narrow-band optical filters. If a light emitting diode is used as a light source, a narrow-band optical filter can be added or not added between the light emitting diode and the optical probe.

The optical probe is shown in FIG. 1 or FIG. 2 . It includes a cavity, an optical signal input and output optical fiber, an optical lens, a bracket for fixing the optical fiber and the lens, and an optical reflector. Water can enter the probe cavity, and the cavity can shield external stray light. The optical probe constitutes an optical pathway. That is, the incident light enters the cavity of the probe through the input optical fiber, and after passing through the lens and the monitored water, the transmitted light (as shown in Figure 1) or reflected light (as shown in Figure 2) is coupled into the output optical fiber of the optical probe, and the output The optical signal is detected by a semiconductor optical wavelength detector.

The semiconductor light wavelength detector is composed of two back-to-back semiconductor p-n junction photodiodes, and the two p-n junctions are aligned with the incident direction of the detected light signal (see Figure 3). During operation, the two p-n junction photodiodes simultaneously detect light signals. The semiconductor optical wavelength detector can have a p-n-p structure (see FIG. 3 ), or an n-p-n structure, or other variant structures composed of these two basic structures. The semiconductor material for making the optical wavelength detector can be silicon, silicon carbide, gallium nitride, gallium arsenide, indium phosphide and other semiconductor materials or their related heterojunction semiconductor materials.

The method for monitoring the water quality is as follows: the optical probe is placed in the water to be monitored or in the water pipe, and the water enters the cavity of the probe. The light with two specific peak wavelengths passes through an optical coupler (such as a two-in-one fiber coupler) or a transmission beam, enters the probe from the input fiber of the optical probe, passes through the monitored water, and transmits the light (as shown in Figure 1 ) or reflected light (as shown in Figure 2) is drawn out by the signal output fiber of the optical probe, and then detected by the semiconductor wavelength detector. When the semiconductor optical wavelength detector is working, the two p-n junction photodiodes detect light signals simultaneously, and the photocurrent ratio of the two p-n junction photodiodes is used to monitor the chromaticity (including ultraviolet absorbance) of the water quality. The size of the photocurrent of a p-n junction photodiode is used to monitor the turbidity of water quality.

Once the chromaticity (including ultraviolet absorbance) of the water quality changes, the light passing through the monitored water will undergo selective absorption, resulting in a change in the central wavelength of the optical signal output from the optical probe. Alternatively, once the turbidity of the water quality changes, the transmittance of light passing through the monitored water will change, resulting in a change in the intensity of the light signal output from the optical probe. After the optical wavelength detector detects that the central wavelength or intensity of the signal light changes, it can send an alarm signal through the control circuit.

(3) Beneficial effect

This water quality monitoring device and method is suitable for remote real-time automatic monitoring of chromaticity, turbidity and COD value of sewage or natural water quality, strong ability to resist interference from running water, weather or other on-site factors, low power consumption, easy operation and maintenance , simple structure and low cost.

4. Description of drawings

Figure 1 Schematic diagram of a transmission optical probe. 1-input and output optical fiber, 2-optical lens, 3-fixing bracket, 4-cavity.

Fig. 2 Schematic diagram of reflective optical probe. 1-input and output optical fiber, 2-optical lens, 3-fixing bracket, 4-cavity, 5-optical mirror.

Fig. 3 Schematic diagram of the structure of the semiconductor optical wavelength detector.

5. Specific implementation

When the present invention is implemented, the optical probe is placed in the monitored water or the water pipe, and the monitored water can enter the optical passage in the optical probe. The light emitted by two light sources with specific peak wavelengths enters the probe through the input optical fiber of the optical probe. After passing through the monitored water, the signal light is drawn out by the output optical fiber of the optical probe, and then detected by the semiconductor optical wavelength detector.

The two light sources with specific peak wavelengths can be two semiconductor light emitting diodes or two semiconductor laser diodes or one ultraviolet lamp plus two narrow-band optical filters. If light-emitting diodes are used as light sources, narrow-band optical filters may or may not be added between the light-emitting diodes and the optical probe;

Two channels of light with specific peak wavelengths pass through the two-in-one fiber coupler, and enter the probe from the signal input fiber of the optical probe. After passing through the lens and the monitored water, the transmitted light is collected by the lens and directly coupled into the signal output fiber of the optical probe ( As shown in Figure 1);

Or two channels of light with a specific peak wavelength pass through a transmission beam, enter the probe from the signal input fiber of the optical probe, pass through the lens and the water to be monitored, and are reflected by a reflector. The reflected light is collected by the lens and coupled into the optical probe. Signal output optical fiber (as shown in Figure 2);

The semiconductor light wavelength detector is composed of two back-to-back semiconductor p-n junction photodiodes, and the two p-n junctions are aligned with the incident direction of the detected light signal (see Figure 3). When working, two p-n junction photodiodes simultaneously detect and read optical signals. The semiconductor optical wavelength detector may have a p-n-p structure (see FIG. 3 ), or an n-p-n structure, or other variant structures composed of these two basic structures. The semiconductor material for making the optical wavelength detector may be silicon, silicon carbide, gallium nitride, gallium arsenide, indium phosphide or related heterojunction semiconductor materials. The ratio of the photocurrents of the two p-n junction photodiodes is used to monitor the chromaticity (including ultraviolet absorbance) of the water quality, and the magnitude of the photocurrents of the two p-n junction photodiodes is used to monitor the turbidity of the water quality.

It should be noted that the above-mentioned embodiments are for illustrating the present invention rather than limiting the patent scope of the present invention, and any equivalent transformation technology based on the present invention shall be within the scope of patent protection of the present invention.

Claims (9)

1. A new type of water quality monitoring device, characterized in that: it comprises a light source with two specific peak wavelengths, an optical probe with signal input and output optical fibers and a semiconductor light wavelength detector that can measure the central wavelength of quasi-monochromatic light. The light emitted by two light sources with specific peak wavelengths enters the optical probe through the input optical fiber of the optical probe. After passing through the water to be monitored, the transmitted light signal is drawn out by the output optical fiber of the optical probe and detected by the semiconductor optical wavelength detector. 2. According to claim 1, the light source with two specific peak wavelengths is characterized in that: two semiconductor light-emitting diodes with specific peak wavelengths, two semiconductor laser diodes with specific peak wavelengths, or an ultraviolet lamp plus two narrow-band optical filter. 3. The optical probe with signal input and output optical fibers according to claim 1, characterized in that it comprises a cavity, an optical signal input optical fiber, an optical signal output optical fiber, and an optical lens. It can also contain optical mirrors. Water can enter the cavity of the probe, and the cavity can shield stray light from outside. 4. According to claims 1 and 3, the optical probe with signal input and output optical fibers is characterized in that: it forms an optical path, and the signal light enters the cavity of the probe through the input optical fiber, passes through the lens and the monitored water, and then transmits The light is collected by another lens and directly coupled into the output fiber of the optical probe; or the transmitted light is reflected by the mirror, then collected by the lens and coupled into the signal output fiber of the optical probe. 5. The semiconductor optical wavelength detector according to claim 1, characterized in that it is composed of two back-to-back semiconductor p-n junction photodiodes, and the two p-n junctions are aligned with the incident direction of the detected optical signal, so A conductive layer (called an intermediate layer) is sandwiched between the two p-n junctions, electrodes are formed on the outer conductive layers of the two p-n junctions, and electrodes are also formed on the conductive intermediate layer. 6. The semiconductor optical wavelength detector according to claims 1 and 5, characterized in that it has a p-n-p structure, or n-p-n structure, or other variant structures composed of the p-n-p or n-p-n basic structure, including the basic structure or Variant structure of integrated optoelectronic circuits. 7. The semiconductor optical wavelength detector according to claims 1, 5 and 6, characterized in that: the semiconductor material used to make the detector is silicon, silicon carbide, gallium nitride, gallium arsenide, steel phosphide or a combination thereof Related heterojunction semiconductor materials. 8. A method for monitoring water quality using the water quality monitoring device described in claim 1, characterized in that: the optical probe as described in claims 1, 3 and 4 is placed in the monitored water or in a water pipe, and water enters the probe In the optical path in the cavity, the light with two specific peak wavelengths described in claims 1 and 2 enters the probe from the signal input optical fiber of the optical probe through the optical coupler, and after passing through the monitored water, the signal light is transmitted by the The signal output fiber of the optical probe is drawn out, and then detected by the semiconductor optical wavelength detector as described in claims 1, 5, 6 and 7. 9. The water quality monitoring method according to claim 8, characterized in that: when the semiconductor wavelength detector as described in claims 1 and 8 is working, the two p-n junction photodiodes as described in claim 5 simultaneously detect optical signals , the photocurrent ratio of the two p-n junction photodiodes is used to monitor the chromaticity (including ultraviolet absorbance) of the water quality, and the photocurrent of the two p-n junction photodiodes is used to monitor the turbidity of the water quality.

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