Evaluation of influent microbial immigration to activated sludge is affected by different-sized community segregation

Activated sludge (AS) microbial communities were analyzed for seasonal variation, a disturbance-recovery event, and separated small aggregates (SAG) to study the influent immigration effect using both neutral immigration model and mass-balance model with operational parameters. SAG differed with AS, and higher immigration impact on SAG was confirmed by both models. Adding the SAG community segregation in the latter model to evaluate the contribution of influent immigration to community disturbance-recovery showed increased impact of immigration.