$-$ Example

$$ Helminth $-$ parasitic intestinal worn

$$ Given : native helminth dp$=50$ micro m$,50$cm depth in clarfier

$$ Find:

$$ How long particle to settle $50$cm$?$

$$ If coagnilant added and dp$=500$micro m$,$ how long to settle $50$cm$?$

$$ Pd $=1\mathrm{.}11$ g$/$cm$^3$

$$ Pw$=0\mathrm{.}9991$g$/$cm$^3$

$$ Uw $=1\mathrm{.}14*10^-3($N$-$s$/$m$^2)$

$$ g$=9\mathrm{.}8$m$/$sec$^2$