You will want to collect some ...
Published by Terry Scheurman, President at Applied Specialties, Inc.
You will want to collect some of the floating material and look at it under a microscope. Great chances you are forming filmentous bacteria. This will be very obvious under a microscope. Another condition is when you are forming N2 and the gas bubbles get trapped on sludge particles. The moment there is increased flow the particles separate and the gas bubbles float the solids.