Ann:

Aelosoma is a transient organism normally found in paper/lumber treatment plants (high SRT as well as having more placid environment) and more than likely was introduced into your plant through the influent.  From what I have seen it will stay in your system between 6-12 months and the concentration will gradually decline.  Also, the solids inventory will decrease by a third and up to a half of your normal operation.  Aelosoma will consume the exterior portion of you flocs (which is a good thing since the exterior of your floc is what is exposed to the environment and suffers the most from toxins and chemicals--just think about grazing sheep)  Depending on the SRT of your system (if it is long then Aelosoma will stay for a longer period of time).  Aeration basins are not a permanent home for Aelosoma.