Sludge bulking (filamentous bacteria) in SBR municipal sewage

Hello,
I'd like to know how to eliminate filamentous bacteria, and how to prevent it from re-growing, in a SBR plant that treats 3400 m3/d of municipal sewage.

The effluent quality meets the environmental norms, however, the excess sludge handling has increasing costs because of the bulking.
Thanks in advance