In General, if you are ...

In General, if you are observing this foam at the inlet of a wastewater treatment works it will most likely be due to surfactants i.e detergents etc in the incoming waste water. This is not likely to be biological at this stage in the process. Depending on the source of the foam, this could transfer through the process and been seen in you final effluent / receiving watercourse, so could cause some environmental concerns. In my experience, surfactants have limited effect on the treatment process, but could cause some issues with foaming in vessels if you have an anaerobic digestion process on site