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Fine-bubble -Porous aluminum oxide or silica is fused into plates or domes.
Medium-bubble – Tubes are covered with perforated saran or fabric socks.
Coarse-bubble – Air is forced through orifices or around rigid or flexible disk.
Surface – Multi-bladed turbines or brushes churn air into the liquid.
Submerged – A sparger feeds air underneath a rotating impeller.
Surface – Multi-bladed turbines in covered tanks churn oxygen into liquid.
Submerged – Compressors recirculate oxygen to spargers in covered tanks.
Porous Turbine – Oxygen goes into rotating porous disks submerged in open tanks.
Cryogenic – compressed air is liquefied by cooling and then distilled into oxygen and nitrogen.
Pressure-Swing Adsorption (PSA) – Vessels of granular media adsorb nitrogen from compressed air, letting oxygen pass through.
Orifice Tube – A rotating tube with orifices picks up the activated sludge.
Multiple Tubes – Several separate tubes on a rotating collector pick up sludge and discharge to the center well.
Traveling Bridge – Some rectangular clarifiers have rolling bridges and pickup tubes with siphons or airlifts.
Chain and Flight – Some smaller rectangular tanks have sprocket-driven scrapers.
Rock or Slag – Chunks with low surface-to-volume ratio are used in shallow standard-rate trickling filters.
Plastic – Corrugated plastic sheets have a high surface area for high-rate treatment or nitrification.
Redwood – Wood slats are used in high-rate filters or activated biofilters.
Rotary – Influent flowing through orifices in the arms pushes them around.
Nozzles – A uniform flat spray pattern is achieved with pumps or siphons.
Rotating Biological Contactors
Motor-drive – Motors rotate each shaft of disks partially submerged in vats.
Air-drive – The shafts rotate as cups on the disk catch diffused air bubbles.