Choosing an appropriate seeding method for wastewater operations can have a significant impact on biological treatment efficiency. Activated sludge is traditionally used to seed new treatment systems and supplement others that need bioaugmentation. A common issue in activated sludge systems is sludge bulking (SB), or the uncontrolled growth of filamentous bacteria (FB).1 Impacts of a bulking sludge include (but are not limited to) poor settleability, impaired biological nutrient removal, and increased facility maintenance.
Predicting whether SB will occur in a newly seeded wastewater process is difficult, because the FB in activated sludge respond differently to varying system conditions. One method to prevent bulking is to quantify the proportion of FB in activated sludge before inoculation. Previous studies have found that SB can occur in systems with a volume fraction of FB as low as 1-20%.