Biological Treatment Of Ammonia In Wastewaters

By Dr. Rakesh Govind

As human population continues to increase, viability of our natural fresh water resources continues to be threatened due to human activities, especially due to changes in the global nitrogen cycle. Use of fossil fuels for energy production, application of nitrogen-based fertilizers, and release of nitrogen compounds in treated sewage water is causing dramatic increases in bio-available nitrogen. Human activity has doubled the amount of global nitrogen fixation, resulting in nutrient imbalances in trees, altering forest health and declines in global biodiversity. Consequences of increased nitrogen availability in the ecosystem has resulted in anoxia (no oxygen) or hypoxia (low oxygen) in marine systems close to the shoreline, altered biodiversity, general habitat degradation due to increased acidification of freshwater ecosystems, and increase in harmful algal blooms.

EPA has recently published revised federal ammonia criteria where the chronic exposure values are much lower than the existing levels, when freshwater mussels are present. States must adopt water quality criteria that protect designated water sources based on EPA's recommended water quality criteria or use other scientifically validated methods.

Ammonia can be separated from wastewater in various ways, which can be classified as either physical, chemical or biological. Physical methods includes: adsorption, vacuum distillation, air stripping, and membrane separation. Chemical methods includes ion exchange and biological approaches biologically oxidize the ammonia to nitrate and nitrite. Generally, physical, chemical methods of ammonia removal are economical when the ammonia concentration is high and the ammonia can be converted to a saleable fertilizer product.