The online automatic monitoring instrument for total nitrogen water quality is a device used for real-time monitoring of total nitrogen content in water bodies. Total nitrogen refers to all forms of nitrogen in water, including ammonia nitrogen (NH3-N), nitrite nitrogen (NO ₂ - N), and nitrate nitrogen (NO 3-N). Monitoring the total nitrogen content in water is of great significance for water quality management and environmental protection. The following is the basic principle and working mode of the online automatic monitoring instrument for total nitrogen water quality.
1. Basic principles
The online automatic monitoring instrument for total nitrogen water quality usually uses chemical analysis or optical analysis to determine the total nitrogen concentration in water samples. The main principles include:
a. Chemical analysis method
Dissolution reaction: Different forms of nitrogen in water samples (such as ammonia nitrogen, nitrite nitrogen, nitrate nitrogen) are converted into ammonia through chemical reactions under certain conditions for subsequent nitrogen determination. Strong acids and oxidants are usually used for the reaction, and common digestive agents include sulfuric acid and hydrogen peroxide.
Distillation or extraction: After digestion, ammonia exists in a free state in the sample and can be separated by distillation or extraction methods.
Chromaticity measurement: The separated ammonia reacts with a chromogenic reagent to generate colored compounds, and their absorbance is measured using a spectrophotometer to calculate the concentration of total nitrogen in the water sample.
b. Optical analysis method
UV absorption method: Some online monitoring devices can use the absorption characteristics of nitrogen compounds in water samples at specific wavelengths in the UV range for measurement. When the water sample passes through the optical path, the instrument emits ultraviolet light of a specific wavelength and measures the change in light intensity after passing through the water sample. The nitrogen concentration is calculated according to the Beer Lambert law.
Fluorescence method: Some advanced monitoring instruments can use the fluorescence characteristics of nitrogen compounds for detection. They use an excitation light source to excite nitrogen compounds in the sample and measure their emitted fluorescence intensity to determine the concentration.
2. Workflow
The following is the general workflow of the online automatic monitoring instrument for total nitrogen water quality:
Water sample collection: The instrument automatically collects water samples from the water body to ensure sample representativeness.
Sample pretreatment: According to the measurement method used, the water sample is subjected to necessary pretreatment, such as digestion, filtering out solid particles, etc.
Determination of nitrogen:
If chemical analysis is used, digestion, distillation, and color reaction are carried out, and finally the absorbance is measured by a spectrophotometer.
If optical analysis is used, nitrogen can be directly determined by UV absorption or fluorescence analysis.
Data processing: The instrument converts the measured signal into nitrogen concentration and displays the results in real-time.
Alarm and recording: When the detected total nitrogen concentration exceeds the set threshold, the instrument will automatically alarm and record data for later analysis and management.
3. Application Fields
The online automatic monitoring instrument for total nitrogen water quality is widely used in:
Monitoring the water quality of natural water bodies such as rivers, lakes, and reservoirs.
Monitoring the effluent quality of industrial wastewater and sewage treatment plants.
Water quality monitoring of water plants to ensure water supply safety.