Analysis and measurement method of ammonia nitrogen in water
Ammonia nitrogen refers to nitrogen in the form of free ammonia (NH3) and ammonium ions (NH4+) in water. The nitrogen content of animal organic matter is generally higher than that of plant organic matter. At the same time, the nitrogen-containing organic matter in human and animal feces is very unstable and easily decomposes into ammonia. Therefore, when the content of ammonia nitrogen in water increases, it refers to the compound nitrogen in the form of ammonia or ammonium ions.
Natural surface water bodies and groundwater bodies are mainly nitrate nitrogen (NO3), and nitrogen in the form of free ammonia (NH3) and ammonium ions (NH4+). The ammonia nitrogen in polluted water bodies is called hydrated ammonia, also called non-ionic ammonia. Non-ionic ammonia is the main factor causing toxicity to aquatic organisms, while ammonium ions are relatively non-toxic. National standard III surface water, the concentration of non-ionic ammonia nitrogen ≤ 1 mg/L. Ammonia nitrogen is a nutrient in water bodies, which can lead to water eutrophication. It is the main oxygen-consuming pollutant in water bodies and is toxic to fish and certain aquatic organisms.
Ammonia nitrogen detection methods usually include Nessler's colorimetry, phenol-hypochlorite (or salicylic acid-hypochlorite) colorimetry and electrode method. The Nessler's reagent colorimetric method has the characteristics of simple operation and sensitivity. The interference determination of metal ions such as calcium, magnesium and iron, sulfides, aldehydes and ketones, color, and turbidity in water requires corresponding pretreatment. The chlorate colorimetric method has the advantages of sensitivity and stability. The interference situation and the elimination method are the same as the Nessler's reagent colorimetric method. Electrode method usually does not require pretreatment of water samples and has the advantages of wide measurement range. When the ammonia nitrogen content is high, distillation-acid titration can still be used.
The ammonia nitrogen in the water can be converted into nitrite under certain conditions. If it is consumed for a long time, the nitrite in the water will combine with protein to form nitrosamines. This is a strong carcinogen and is extremely harmful to human health. The main harmful effect of ammonia nitrogen on aquatic organisms is free ammonia, which is dozens of times more toxic than ammonium salts, and increases with the increase in alkalinity. The toxicity of ammonia nitrogen is closely related to the pH value and water temperature of the pool water. In general, the higher the pH value and water temperature, the stronger the toxicity, and the harm to fish is similar to nitrite.
The harm of ammonia nitrogen to aquatic organisms can be divided into acute and chronic. The hazards of chronic ammonia nitrogen poisoning are: reduced food intake, slower growth, tissue damage, and reduced oxygen transport between tissues. Fish are more sensitive to ammonia nitrogen in water, and high levels of ammonia nitrogen will cause fish death. The hazards of acute ammonia nitrogen poisoning are: aquatic organisms are excited, lose their balance in the water, convulsions, and even die in severe cases.
The ammonia nitrogen sensor itself has an internal signal adjustment function, which can make the data signal more stable and accurate, so that the maximum distance between the data recorder and the data recorder can be up to 200 meters. There is an NPT thread on the back of the sensor, which is easy to install and fix on an object. The sensor's waterproof grade is IP68. The port has an electrode protective cover, which can be removed when replacing the electrode. The sensor cable cannot be used as a load-bearing cable and cannot be immersed in water.
Finally, I will introduce to you the water quality sensor imported from the American ECD company by the famous sensor online shopping mall. It is also called the ammonia nitrogen sensor-HYDRA NH4+-N, which is a three-electrode system using a spray cleaner. Ammonium ammonium (NH +-N) is the main measurement method. Potassium ion and pH glass electrodes are used to compensate the NH4+ signal. The sensor is waterproof, and its input level is ip68.
Three advantages of ammonia nitrogen sensor:
1. Fast and accurate ammonium ion measurement NH4+ or NH4+-N completely compensates for pH, K+ interference and temperature. Removable electrode protection is easy to maintain.
2. Clean the sensor with pressurized water or air.
3. The amplified signal is allowed to reach 200 meters between the sensor and the analyzer.
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