Figure $1$: Two$-$stage split treatment.

If the alternative plan is to soften the water using an lon exchange, would it be cheaper

than lime$-$soda softening? Assume that the price of resin is $$2$ per $kg,$ and it needs to be

replaced two times annually. The pilot test with ion exchange generated the following. Please help

data $($Table $4).$ The pilot$-$scale column was operated at a flow rate of $0\mathrm{.}15\frac{m^3}{h}$ with a

residence time of $4\mathrm{.}68$min. According to the manufacturer's specifications, the resin has

$60\%$ moisture content and $0\mathrm{.}75k\frac{g}{m^3}$ density.