Often I have seen people confuse nitrification and denitrification during conversation. In the last post, I covered nitrification which is the conversion of ammonium (ammonia nitrogen) into nitrate via a two-step biological pathway. The organisms in the nitrification process are most commonly Nitrosomonas sp. and Nitrobacter sp. (There are other microbes, but they occupy the same ecological niche and have similar growth characteristics). Key points are the nitrification microbes are:
When it comes to nitrate/nitrite removal the following conditions are needed:
Denitrification can also be a problem when there is excessive nitrate in the secondary clarifier. If the solids are held in the clarifier too long (usually >3 hours) - the bacteria can use the nitrate to degrade adsorbed organics. The sludge then floats to the top of the clarifier and can carry over the weir. In this case the most often used solution is to increase recycle rates which lowers residence time in the clarifier.
Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.
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