Water quality monitoring device and monitoring method thereof

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.