Gas bubbles in WWTP are generated by aeration, mechanic mixing and biological process like denitrification and anaerobic digestion Surfactants in WWTP come from the wastewater streams that contain slowly biodegradable surfactants hydrophobic particles are normally referred to the filamentous bacteria with a long-chain structure and hydrophobic surface. Meanwhile, the particles also serve as collector for surfactant which stabilizes the foam. The hydrophobic particles congregate at the air-water interface and strengthen the water film between air bubbles. Stable foaming in WWTP is the product from interaction among gas bubble, surfactant and hydrophobic particles. household detergents) from industrial or municipal wastewater, excess production of extracellular polymeric substance (EPS) by activated sludge microorganisms under nutrient-limited condition, proliferation of filamentous organisms and gas provided in aeration tank or produced in anoxic zone of aeration tanks, secondary clarifiers and anaerobic digesters. Many reasons are associated with foaming: presence of slowly biodegradable surfactants (eg. The foam can also overflow onto walkways and surrounding areas, posting severe difficulties and risk to operation and environment.Īctivated sludge foaming in aeration tank. It floats and accumulates on top of the tanks, and can take up a large fraction of solids inventory and reactor volume, thus decreasing the effluent quality and control of sludge retention time (SRT). Foam in WWTP is normally sticky, viscous and brown in color. The foam can occur in aeration tank, secondary clarifier, as well as in anaerobic digester. 6.2 Development of Effective Foaming-Control Chemicalsįoaming in activated sludge process is a common operational problem in many wastewater treatment plants.

6.1 Identification of Filamentous Bacteria.

4.2 Cell Surface Hydrophobicity and Exoenzyme Activities.

Bulking and cutting waste