One set of bacteria grow in the absence of oxygen and one with oxygen. that is why biologic reactors in a sewage treatment plant have aeration zones and covered zones. chek out websites for SDanitaire aeration equipment.
Also you may Google "biological reactors" and get some details.
“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
Common BNR Configurations use a Five-Stage Bardenpho process. The result is the development of a different sludge in each of
the stages. The tank in which the biological reactions take place is referred to as a bioreactor. Over the years, several bioreactor configurations have been developed to achieve TN and TP removal. All of them incorporate the anaerobic, anoxic, and aerobic zones. The differentiating features are the zone sequence and location of the recycle streams.
Anoxic refers to the presence of combined oxygen (nitrate and nitrite) and the absence of free or dissolved oxygen (DO).
Biological phosphorus removal can be accomplished by placing an adequately sized anaerobic zone ahead of the aerobic zone to
favor the growth of phosphorus-removing organisms. Facilities that have turned off the air supply in an effort to create an anaerobic
selector at the beginning of the bioreactor have accomplished fairly good phosphorus removal.
