The instability of ammonia nitrogen (NH3-N) in wastewater mainly refers to the fact that ammonia nitrogen may exist in the form of free ammonia (NH3) and ionic ammonia (NH4+) in water, and the equilibrium between the two is affected by pH value and temperature. Free ammonia is toxic to aquatic organisms and can lead to eutrophication of water bodies, so appropriate methods need to be taken to remove ammonia nitrogen from wastewater. Here are some common ways to remove ammonia nitrogen:
1.*Biological Nitrogen Removal**:
Biological nitrogen removal is the conversion of ammonia nitrogen into nitrogen gas by the action of microorganisms, which is removed from wastewater. This process typically consists of two stages: nitrification and denitrification. Nitrifying bacteria oxidize ammonia nitrogen to nitrite (NO2-) and nitrate (NO3-), while denitrifying bacteria reduce these nitrogen compounds to nitrogen.
2.*Air Blow-off**:
Air blowing is the process of blowing air into wastewater to remove ammonia nitrogen from water. This method is suitable for high concentrations of ammonia nitrogen, but the treatment of ammonia after blowing needs to be considered.
3.*Chemical precipitation**:
Ammonia nitrogen is combined with metal ions to form an insoluble precipitate by adding chemical reagents (such as iron sulfate or aluminum sulfate) to the wastewater, which is then removed by solid-liquid separation.
4.*Ion exchange**:
Ion exchange resins are used to remove ammonia nitrogen from wastewater. The functional groups on the resin exchange with ammonia nitrogen, thereby removing ammonia nitrogen.
5.*Membrane Separation Technology**:
Through nanofiltration, reverse osmosis and other membrane technologies, the selective permeability of semi-permeable membranes is used to realize the separation of ammonia nitrogen and water.
6.*Electrochemical Oxidation**:
Ammonia nitrogen is oxidized into nitrogen or other harmless substances by electrochemical reactions.
7.*Breakpoint chlorination**:
Chlorine is added to the wastewater, and the chlorine reacts with ammonia nitrogen to produce nitrogen and chloride. This method is simple to operate, but it is expensive and can produce chlorination by-products.
Each method has its scope of application, advantages and disadvantages, and the most suitable treatment technology needs to be selected according to the concentration of ammonia nitrogen in the wastewater, water quality characteristics, economic cost and environmental protection requirements. At the same time, the relevant environmental protection regulations and standards should be strictly observed during the treatment process to ensure the treatment effect and protect the environment.