Water quality monitoring device and monitoring method thereof
A water quality monitoring device and a monitoring method thereof are provided. The water quality monitoring device includes a water tank, a first and a second optical detection devices and a control circuit. The water tank has an accommodating space to carry a liquid. The first optical detection device provides a first light to detect and obtain a first reference light intensity, a first scattered light intensity, and a first penetrating light intensity. The second optical detection device provides a second light to detect and obtain a second reference light intensity, a second scattered light intensity, and a second penetrating light intensity. The control circuit calculates a water quality detection value of the liquid based on the first reference light intensity, the first scattered light intensity, the first penetrating light intensity, the second reference light intensity, the second scattered light intensity, and the second penetrating light intensity.
1 . A water quality monitoring device, comprising:
a water tank, having an accommodating space to carry a liquid;
a first optical detection device, comprising:
a first light emitter, providing a first light, wherein the first light is incident into the accommodating space of the water tank;
a first reference light receiver, detecting a light intensity of the first light before the first light is incident into the accommodating space, so as to obtain a first reference light intensity;
a first scattered light receiver, receiving a scattered light in the first light through the accommodating space of the water tank to detect and obtain a first scattered light intensity of the first light; and
a first penetrating light receiver, receiving a penetrating light in the first light through the accommodating space of the water tank to detect and obtain a first penetrating light intensity of the first light;
a second optical detection device, comprising:
a second light emitter, providing a second light, wherein the second light is incident into the accommodating space of the water tank, and the first light and the second light have different wavelengths;
a second reference light receiver, detecting a light intensity of the second light before the second light is incident into the accommodating space, so as to obtain a second reference light intensity;
a second scattered light receiver, receiving a scattered light in the second light through the accommodating space of the water tank to detect and obtain a second scattered light intensity of the second light; and
a second penetrating light receiver, receiving a penetrating light in the second light through the accommodating space of the water tank to detect and obtain a second penetrating light intensity of the second light; and
a control circuit, electrically coupled to the first optical detection device and the second optical detection device,
wherein the control circuit calculates a water quality detection value of the liquid based on the first reference light intensity, the first scattered light intensity, the first penetrating light intensity, the second reference light intensity, the second scattered light intensity, and the second penetrating light intensity;
wherein the control circuit is further configured to:
estimate an initial value of the first penetrating light intensity of the first light, an initial value of the second penetrating light intensity of the second light, a light absorbance coefficient of chemical oxygen demand (COD) of the second light, a light absorbance coefficient of suspended solid (SS) of the first light and a light absorbance coefficient of SS of the second light by using a standard product;
measure and correct the first penetrating light intensity corresponding to the first light and the second penetrating light intensity corresponding to the second light in the liquid;
calculate a light absorbance of total chemical oxygen demand (CODt) in the liquid in the second light according to the initial value of the second penetrating light intensity and the corrected second penetrating light intensity corresponding to the second light;
calculate a light absorbance of SS in the liquid in the first light according to the initial value of the first penetrating light intensity and the corrected first penetrating light intensity corresponding to the first light, and calculate a light absorbance of the SS in the liquid in the second light according to the light absorbance coefficient of the SS of the first light, the light absorbance coefficient of the SS of the second light and the light absorbance of the SS in the liquid in the first light;
deduct the light absorbance of the SS in the liquid in the second light from the light absorbance of the CODt in the liquid in the second light to calculate a light absorbance of CODs in the liquid in the second light; and
calculate a concentration of the CODs in the liquid according to the light absorbance of the CODs in the liquid in the second light, the light absorbance coefficient of the COD of the second light and a measurement optical path, or calculating a concentration of the SS in the liquid according to the light absorbance of the SS in the liquid in the first light, the light absorbance coefficient of the SS of the first light and the measurement optical path.
2 . The water quality monitoring device according to claim 1 , wherein the water quality detection value is one of a concentration of a soluble chemical oxygen demand (CODs) and a concentration of a dissolved organic carbon (DOC).
3 . The water quality monitoring device according to claim 1 , wherein the first light is incident into the accommodating space of the water tank in an incident direction, and an angle between the incident direction and a detection direction of the first penetrating light receiver is 180 degrees,
an angle between the incident direction and a reference light detection direction of the first reference light receiver is 90 degrees, and
an angle between the incident direction and a scattered light detection direction of the first scattered light receiver is one of 30 degrees to 150 degrees.
4 . The water quality monitoring device according to claim 1 , wherein the second light is incident into the accommodating space of the water tank in an incident direction, and an angle between the incident direction and a detection direction of the second penetrating light receiver is 180 degrees,
an angle between the incident direction and a reference light detection direction of the second reference light receiver is 90 degrees, and
an angle between the incident direction and a scattered light detection direction of the second scattered light receiver is one of 30 degrees to 150 degrees.
5 . The water quality monitoring device according to claim 1 , wherein the first reference light receiver comprises a detection end, and the detection end is within 1 cm from a light emission end of the first light emitter.
6 . The water quality monitoring device according to claim 1 , wherein the second reference light receiver comprises a detection end, and the detection end is within 1 cm from a light emission end of the second light emitter.
7 . The water quality monitoring device according to claim 1 , wherein the first reference light receiver comprises a detection end, and the detection end is within 5 mm from a vertical distance of an optical axis of the first light.
8 . The water quality monitoring device according to claim 1 , wherein the second reference light receiver comprises a detection end, and the detection end is within 5 mm from a vertical distance of an optical axis of the second light.
9 . The water quality monitoring device according to claim 1 , wherein the first light emitter is a visible light emitter or an infrared light emitter, and the second light emitter is an ultraviolet light emitter.
10 . A water quality monitoring method using the water quality monitoring device claimed in claim 1 for monitoring water quality, and the water quality monitoring method comprising:
providing the first light to detect and obtain the first reference light intensity, the first scattered light intensity, and the first penetrating light intensity;
providing the second light to detect and obtain the second reference light intensity, the second scattered light intensity, and the second penetrating light intensity; and
calculating the water quality detection value of the liquid based on the first reference light intensity, the first scattered light intensity, the first penetrating light intensity, the second reference light intensity, the second scattered light intensity and the second penetrating light intensity;
wherein the step of calculating the water quality detection value of the liquid based on the first reference light intensity, the first scattered light intensity, the first penetrating light intensity, the second reference light intensity, the second scattered light intensity and the second penetrating light intensity comprises:
estimating an initial value of the first penetrating light intensity of the first light, an initial value of the second penetrating light intensity of the second light, a light absorbance coefficient of chemical oxygen demand (COD) of the second light, a light absorbance coefficient of suspended solid (SS) of the first light and a light absorbance coefficient of SS of the second light by using a standard product;
measuring and correcting the first penetrating light intensity corresponding to the first light and the second penetrating light intensity corresponding to the second light in the liquid;
calculating a light absorbance of total chemical oxygen demand (CODt) in the liquid in the second light according to the initial value of the second penetrating light intensity and the corrected second penetrating light intensity corresponding to the second light;
calculating a light absorbance of SS in the liquid in the first light according to the initial value of the first penetrating light intensity and the corrected first penetrating light intensity corresponding to the first light, and calculating a light absorbance of the SS in the liquid in the second light according to the light absorbance coefficient of the SS of the first light, the light absorbance coefficient of the SS of the second light and the light absorbance of the SS in the liquid in the first light;
deducting the light absorbance of the SS in the liquid in the second light from the light absorbance of the CODt in the liquid in the second light to calculate a light absorbance of CODs in the liquid in the second light; and
calculating a concentration of the CODs in the liquid according to the light absorbance of the CODs in the liquid in the second light, the light absorbance coefficient of the COD of the second light and a measurement optical path, or calculating a concentration of the SS in the liquid according to the light absorbance of the SS in the liquid in the first light, the light absorbance coefficient of the SS of the first light and the measurement optical path.
11 . The water quality monitoring method according to claim 10 , wherein the control circuit has an initialized first reference light intensity preset value corresponding to the first reference light receiver and an initialized second reference light intensity preset value corresponding to the second reference light receiver,
and the step of measuring and correcting the first penetrating light intensity corresponding to the first light and the second penetrating light intensity corresponding to the second light in the liquid further comprises:
calculating a correction value of the first penetrating light intensity according to the first reference light intensity preset value, the first reference light intensity, and the first penetrating light intensity; and
calculating a correction value of the second penetrating light intensity according to the second reference light intensity preset value, the second reference light intensity, and the second penetrating light intensity.