nocardia bacteria

[DON KRESS]

I am a layperson in this subject so forgive any biological inaccuracies 
please.

A problem with the local municipal sewage water treatment plant is 
occurring in my area and an organism they said had been identified as 
"nocardia filamentous bacteria" is the culprit.  The effect the 
organism's growth has is to cause a brownish foam several inches thick to 
appear on the surface of the water in the clarifier tanks which is a 
final stage of the water treatment process.  The surface skimming rakes 
that the tanks are equipped with are not designed to handle this 
thickness and consistency of foam.  The net result is foam carryover into 
the effluent stream.  This is environmentally unacceptable and they are 
looking at remedial measures such as physically removing the foam using 
vacuum trucks on a temporary basis and improved surface skimming 
equipment for the long term.

The problem has been a recurring one over the last ten years and is as 
bad as it has ever been right now.  The plant operators have not been 
able to establish a cause and effect relationship to explain this 
phenomena.  A mechanism that was described is that this bacteria attaches 
itself to oil and\or grease and floats it to the surface.  The plant has 
a high throughput and the sewage has a short residence time.

My focus is to attempt to identify the root cause of the problem.  
Presumably this bug is always present and will grow to objectionable 
levels only under certain conditions.

Questions:

Am I in the right newsgroup?

Has anyone seen this sort of effect in a sewage treatment plant and was 
the root cause identified?

Are there certain compounds in the sewage water entering the plant that 
would cause this organism to proliferate?

Could waste water from petroleum refining which may contain miscellaneous 
trace amounts of hydrocarbon compounds create favourable growth 
conditions for this organism?

Any tips on other questions jor things I should be considering?

Any references to other souces of information would be appreciated!

DEKress
Ontario
Canada