pop$=200,000,$ water supply $=140$l$/$day $,$ back wash $=5\%,$ area filter $=40$m$2,$ filtration rate $=15$m$/$day $,$ filter expanling by $=0\mathrm{.}66$m $,$ porasty $=0\mathrm{.}5$

cd $=5\mathrm{.}62$

d$=1\mathrm{.}004*10^-6$ m$/$s $,$ depth $=0\mathrm{.}8$ m

dp$=0\mathrm{.}6$ mm

sg$=2\mathrm{.}5$

find$1.$ Ee $($porosty e$)$

$2.$through design

$3.$ hl during expansion

$4.$ hl during filtration