Activated sludge process is a biological process that is widely used in the domestic and
industrial wastewater treatment in over the world. The foam formation is often reported in
wastewater treatment plants which are related to this process. Some operational problems can be
created by foaming, such as effluent quality deteriorates, the creation of malodorous, increased time
requirements in order to plant maintenance, and in extreme cases, hazardous working conditions
resulting from foam spilling out of the aeration basin and as well as increased in operational costs.
There are different ways to overcome this problem, such as reduce air flows into the aeration basin,
reduction in the grease and oil content of the wastewater, surface and return activated sludge (RAS)
chlorination, anoxic and anaerobic selectors, solid retention time (SRT) control and antifoams and
organic polymer addition. On the other hand, rapid and accurate identification of the foam causes
is in the first step to control bulking and foaming. Foam problem is often created by filamentous
bacteria, such as
Nocardia and
Gordonia
species. This bacterium has a role important in activated
sludge.
