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[[File:Maxresdefault.jpg|thumb|700px|A plan view example of what an Oil-Grit Separator (OGS) pretreatment device looks liked. The tapering cylinder chamber creates a "vortex swirling effect", which allows sedimentation to take place a deposits particles at the bottom of the chamber, the flow breaker grate also aids in sedimentation of suspended particles to to settle at the bottom of the sludge chamber to later be cleaned by maintenance staff (3P Technik UK Ltd, n.d.)<ref>3P Technik UK Ltd. n.d. HYDROSHARK – ADVANCED HYDRODYNAMIC PARTICLE SEPARATOR. Stormwater Treatment. Accessed September 20 2023. https://www.3ptechnik.co.uk/stormwater-treatment/hydroshark-particle-separator//</ref>]]

[[File:OGS example.jpg|thumb|450px|Plan view cut out of a typical Oil-Grit Separator (OGS) pretreatment device. In this example, the cylinder chamber and weirs create a "vortex swirling effect", which promotes settling of solids in the bottom of the chamber.  In most OGS, there is also an oil storage chamber to capture light liquids and floatables. The accumulated sediment and debris is cleaned out regularly by maintenance professionals once the sediment in the chamber reaches the manufacturer’s recommended sediment maintenance depth or the floatables capture chamber is full.]]

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