Well that depends on bed ...

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Well that depends on bed depth, media size (d10) and uniformity coefficient. A 24" bed of 0.5 mm ES sand running at 10 gpm/ft2 takes out around 35% of 3-5 micron particles depending on water TDS, pH, DOC and a bunch of other factors that influence particle filterability.

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Usually it it 5-10 micron, depending on media size and depth. Particles smaller than 5 micron can only be removed by the granular media filter if they are coagulated and flocculated into larger particles. Membrane filters (MF/UF) can remove much smaller particles (<0.1 micron) without the need for coagulation.

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Dear Joe. Thank you very much for your attention to this question.The objective is to explore which is the opinion of experts on the topic in order to design an experiment to determine if rapid sand filtration preceded by good coagulation - floculation - sedimentation stages is capable of retaining small particles (<0.5µ) and challenge this vs the DBP's rule that aims to remove DOC which is <0.45µ particles. If the current filtration technique used around the world even when using enhanced coagulation is not capable to remove <0.5µ particles then we can conclude that this technique dated back to 1900 is obsolete and that is time to look for another options for TTHM control.

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