Symptoms

• Scum presence in the aeration basin

Main causes

• High content of foaming agents and/or oils and greases in the incoming wastewater

Investigations and analyses

• Evaluate the presence of Nocardia in the mixed liquor and in the foam

• Evaluate oil and grease in the influent wastewater

• Evaluate temperature oscillation in the aeration basin

Remedial actions

• Foam removal through water sprinkling

• Chlorine dosage