Sand grading in Slow sand filters

[ch81pc]

Can anyone give me some ball-park figures for the d10, d30 and d60 sieve sizes for media used in a slow sand filter?
I have anaylsed the sand currently used at my plant and believe it to be too fine, but need some other gradings for comparison. Thanks

Paul

 

[bimr]

The following report has a survey of installation that list some of the details on the filters. Effective filtration methods for small water supplies / John L. Cleasby ... [et al.].
Cincinnati, OH : U.S. Environmental Protection Agency, Municipal Environmental Research Laboratory : Center for Environmental Research Information [distributor], 1984.

Sand effective sizes ranged from 0.15 to 0.40 )with 0.30 mm most common), sand uniformity coefficents from 1.5 to 3.6 (with 2 most common) and initial bed depths from .46 to 1.52 m (with 0.9 m most common). Most common filtration rates 0.07 to 0.12 m/h. This installations were all in the US.