The surface water naturally contains ammonia nitrogen and is applied to cultivated land in the form of nitrogen fertilizer. And a large number of synthetic fertilizers that are not used by crops are brought into groundwater and surface water by farmland drainage and surface runoff. As a decomposition product of nitrogen-containing organic matter, it is the main reason why ammonia is widely present in rivers, lakes and seas. However, its concentration in groundwater is very low because it is adsorbed on soil particles and clay, and is not easily leached from the soil. According to preliminary estimates of agricultural non-point source emissions, the eutrophication load of total nitrogen and total phosphorus in rural areas accounted for about 60%.
The excrement of aquatic animals, fertilizers, residual bait, and animal and plant carcasses are decomposed into amino acids by microorganisms, and then further decomposed into ammonia nitrogen; when oxygen is insufficient, nitrification occurs in the water body, and nitrite and nitrate are decomposed under the action of denitrifying bacteria. Ammonia nitrogen; fish discharge ammonia nitrogen in the body into the water.
1. High dissolved oxygen content will accelerate the oxidation process of molecular ammonia and nitrite nitrogen, so that it can be converted into non-toxic nitrate nitrogen as soon as possible. Therefore, once the ammonia nitrogen and nitrite content in the water body are found to exceed the standard, attention should be paid to start more aerators, or use chemical oxygenators to increase the dissolved oxygen level in the pond.
2. Beneficial bacteria in the water body such as photosynthetic bacteria, nitrifying bacteria, bacillus, etc. can decompose ammonia nitrogen and nitrite and reduce the accumulation of toxic nitrogen-containing waste. It can be added artificially to degrade ammonia nitrogen and nitrite.
3. The pH of the water body. The pH of water directly affects the dynamic balance between molecular ammonia and ionic ammonia in the water, when the pH is high. The concentration of molecular ammonia will increase, resulting in an increase in the toxicity of ammonia nitrogen. When the water body contains high ammonia nitrogen, lime must not be used for disinfection, so as to avoid ammonia nitrogen poisoning.
4. Nitrite is an intermediate product in the oxidation process of nitrogen-containing substances. It is very unstable. The content of nitrite in rainwater, especially after electricity, will increase.
So how to detect the ammonia nitrogen content in the water? The following introduces two national standard methods with simple operation and accurate data. No professional knowledge is required, and the results can be detected very well.
1. Salicylic acid method (HJ 533-2009);
Detection principle: In the presence of alkaline medium (pH =11.7) and sodium nitroferricyanide, ammonia and ammonium ions in water react with salicylate and hypochlorite ions to form blue compounds.
Operation process: Take a clean colorimetric tube, add the water sample to be tested to the 15mL scale line of the tube, add a package of ammonia nitrogen reagent (I), cover the lid and shake to dissolve, after 2 minutes, add a package of ammonia nitrogen reagent II ), close the lid and shake to dissolve it, leave it for 15 minutes, open the lid, and place the colorimetric tube on the colorimetric card. The upper blank space is compared with the standard color scale from top to bottom, and the color of the solution in the tube is the same The color scale is the content of ammonia nitrogen in the water (mg/L).
Application industry: The salicylic acid method can detect sea water because of its low detection limit. It is widely used in aquaculture, aquarium, marine park, underwater world, domestic fish tank and ornamental fish water detection. Untitled-1
2. Nano reagent method (HJ 533-2009);
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 whose absorbance is proportional to the content of ammonia nitrogen.
Operation process: 1. Add 1ml of the water sample to be tested into the matching small test tube 2. Add 4 drops of the matching reagent, close the lid and shake well 3. Take a test paper and immerse it in the small test tube for 10 seconds 4. Shake off the excess on the test paper The solution is immediately compared with the color chart pair
Industry application: Because of its wide range, the Na-type method produces data quickly. It is widely used for wastewater testing in printing and dyeing factories, textile factory wastewater, environmental protection projects, sewage treatment plants and other industries.
3. The accuracy requirements are relatively high, a tester can be selected, and the operation and reading are more convenient. It can measure up to 50mg/L. It can meet the requirements of most sewage testing. The measurement range is relatively large and can be measured after diluting with pure water. Then multiply the dilution factor of the water sample.
(1.) Estimate the ammonia nitrogen content of the water sample and select an appropriate range.
(2.) Add zero water sample according to the corresponding range:
When the water sample content is 0-5mg/L (ammonia nitrogen 0-5):
①Draw 10mL (at the scale line) of the water sample to be tested and pour it into the cuvette, and set the instrument to zero.
When the water sample content is 0-50 mg/L (ammonia nitrogen 0-50):
①Draw 1mL water sample and 9mL purified water into the cuvette, and adjust the instrument to zero.
(3.) Take out the cuvette, add 6 drops of activator (A) and shake well, then add 6 drops of activator (B) and shake well. Countdown to react for 3 minutes and read.