The bacteria responsible for most ammonia and nitrite removal in wastewater treatment systems - new data
In most of my training and consulting materials, I have spoken of nitrification as a combination of two distinct microbial genera - Ammonia oxidizing Bacteria (AOB) and Nitrite Oxidizing Bacteria (NOB) - which were normally listed as Nitrosomonas sp. (AOB) and Nitrobacter sp. (NOB). Other genera were mentioned but considered secondary (if ever mentioned). The organisms and reactions are given below:
What we have been teaching is not exactly correct in most wastewater systems! With more advanced genetic testing, we have found that most chemoautotrophic nitrification is being done by Nitrospira sp. which can do both steps. Therefore, Nitrospira can be thought of as AOB & NOB cultures. Nitrosomonas are much less common (lower percentage of total reads in testing).
No matter which organisms are removing ammonia and nitrite, the following checklist comes from working wastewater treatment plants that achieve ammonia and nitrite oxidation.
pH 6.5-8.5, 7.2 - 7.8 is optimum for MLSS
Temperature 10 - 38 Deg C, 30 Deg C optimum
Effluent BOD5 < 30 mg/L
Effluent COD <100-150 mg/L
Effluent TOC <45 mg/L
MLSS 2,500 mg/L
Sludge Age (MCRT) 5 - 15 days
DO >2.0 mg/L, 2.0 - 4.0 in systems subject to shock
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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