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Self-Cleaning Externally Fed Rotary Drum Screen

The Muffin Monster Externally Fed Rotary Drum Screen is a reliable self-cleaning wedge wire screen for municipal wastewater operations. This screening technology performs particularly well in wastewater with high oil or grease loadings as well as scum applications that can blind other types of screens. It is used for fine screening primary sewage influent at the headworks as well as screening of clarifier scum.

The RSS Externally Fed Rotary Drum Screen is constructed of slotted stainless wedge wire formed into a cylindrical drum that rotates on two pillow block bearings. The screen typically has openings ranging from 0.100 to 0.010 inches and features 100% overflow protection from blinding for flows up to 5.0 mgd.


  • 100% overflow protection for designed flow up to 5.0 mgd
  • More material recovery for reuse
  • Customized to fit into existing infrastructure


  • All 304 stainless steel construction
  • Solid unitary frame
  • Wedge wire drum
  • Doctor blade assembly with Monel blade
  • Internal spray bar


  • Flows from 110 to 4000 GPM
  • Drum diameters from 25 to 36 inches
  • Drum lengths from 12 to 120 inches

Method of Operation

Raw influent enters a headbox which distributes the flow evenly across the full length of the rear, upper external surface of the rotating drum screen. As water passes through the screen, solids are retained on the outside of the screen drum and are carried by rotation to the front of the screen where they are removed by a fixed doctor blade. The screened water cascades down inside the drum and falls through the bottom, creating a vigorous backwash action. This action, together with the use of internal water sprays, has a combined effect to self-clean the drum on every revolution.

Screened solids can then be discharged into a dumpster, washer compactor or conveyor.