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Case Study: Primary Clarifier Scum Mixing

“All Clarifiers Should Not Be Without!”


Problem: The wastewater utility had to monthly manually vactor out the scum that accumulates from fats, oils and grease trapped in the primary scum trough which was costly, odorous and messy. The existing scum pumps would only pump out the clear liquid beneath leaving a floating scum mat that built up and needed to be vactored out.

BEFORE: Primary Scum Sludge Closeup

BEFORE: Primary Scum Sludge















Solution: In the scum pit, installed a Flygt compact 2.5HP submersible mixers on a timer and set to turn on prior to operation of scum pump. The fats, oils, grease (FOG) and floatables are entrained and pumped away and no more need to manually vactoring out four scum pits monthly.

AFTER: Flygt Submersible Mixer mixes Primary Scum


A Flygt pump with N-hydraulics was installed to retrofit screw induced pumps. The Flygt’s self cleaning impeller to handle the challenging scum/debris without clogging.

Flygt’s Self-Cleaning Pump ideal for handling Primary Scum without clogging