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