The most concerned forms of nitrogen in water and wastewater are nitrate ammonia, nitrite nitrogen, ammonia nitrogen and organic nitrogen. Through biochemical action, they can be transformed into each other. Ammonia nitrogen digestion process-Lu Heng
According to the "Surface Water Environmental Quality Standards" (GB 3838-2002) published by the Ministry of Ecology and Environment of the People's Republic of China, it specifies Class III surface water with an ammonia nitrogen concentration of ≤1 mg/L. The Comprehensive Wastewater Discharge Standard (GB8978-1996) stipulates that the average discharge unit ammonia nitrogen emission shall be ≤15mg/L (primary discharge standard) and ≤25mg/L (secondary discharge standard).
So how to quickly determine the ammonia nitrogen content in water? The following introduces two national standard methods with simple operation and accurate data. No professional knowledge is required to detect the results.
1. Salicylic acid method
Detection principle: In the presence of an alkaline medium (pH = 11.7) and sodium nitroferrocyanide, ammonia and ammonium ions in the water react with salicylate and hypochlorous acid ions to form a blue compound.
Operation process: Take a clean colorimetric tube, add the water sample to be measured to the 15mL scale of the tube, add a packet of ammonia nitrogen reagent (I), cover and shake to dissolve, add a packet of ammonia nitrogen reagent II after leaving for 2 minutes ), cover the lid and shake to dissolve. After 15 minutes, open the lid and place the colorimetric tube on the colorimetric card. The upper blank space is visually compared with the standard color scale from top to bottom. The color scale is the content of ammonia nitrogen (mg/L) in the water.
Application industry: The salicylic acid method can detect seawater because of its low detection limit. Widely used in aquaculture, aquarium, marine park, underwater world, household fish tank ornamental fish water detection.
2. Nano reagent method
The detection principle is that ammonia nitrogen in the form of free ammonia or ammonium ions reacts with Nessler's reagent to form a reddish-brown complex. The absorbance of the complex is proportional to the ammonia nitrogen content.
(1.) Add 1ml of water sample to be tested in the matching small test tube
(2.) Add 4 drops of matching reagents, cover and shake well
(3.) Take a test paper and immerse it in a small test tube for 10 seconds
(4.) Throw away the excess solution on the test paper and immediately compare it with the color chart.
Industry application: Because of its wide range, the Nano method has fast data output. Widely used in wastewater testing in printing and dyeing factories, textile mill wastewater, environmental protection projects, sewage treatment plants, etc.