First thing is to get the ...

First thing is to get the filaments identified.  If it is nocardia, then the best way to deal with it is managing it as opposed to trying to kill it.  It is a constant battle with nocardia.  Here in the UK we tend to find nocardia due to the influent characteristics containing FOG, typically in tourist catchments with a high density of hotels, B&Bs, restaurants etc.  You need good trade effluent management, the properties need to keep their grease traps well maintained.  Even with this the inlet works will still need FOG removal and it is best to have a classifying selector. This is not your traditional type of selector - a floating boom in the aeration lane which the operator can isolate and remove the moose which contains the nocardia.  This type of device is still quite novel but easy to build in for new builds.  By removing it this way you are in effect managing it but at a lower cost than constantly dosing something into the process. Nocardia is more a nuisance than a problem especially in warmer months when it can crust over and cause foul odours.