6.30 Water softening: Reagent needs and sludge formation Water containing 150 g mof Ca2* and 75 g m-3 of HCO, alkalinity is to be softened using the lime-soda process. (a) For a water flow rate of 1 m s-l, calculate the daily chemical requirements of lime (Ca(OH)2) and soda (Na,CO,) (metric tons per day). (b) Calculate the rate of generation of sludge solids mass (metric tons per day). (c) Calculate the net change in total dissolved solids (TDS, g m) caused by softening.