A groundwater was analyzed and found to have the following composition: HCO3- = 185 mg/L as CaCO3; Mg2+ = 66 mg/L as CaCO3 ; Ca2+ = 149 mg/L as CaCO3; H2CO3 = 29 mg/L as CaCO3

a) Determine the lime and soda ash dose in mg/L CaCO3

b) If the price of lime, purchased as CaO, is $65 per ton, and the price of soda ash, purchased as Na2CO3, is $180 per ton, estimate the annual chemical cost of treating 1.0 m3/s of this water. Hint: One mole of CaO equals one mole of Ca(OH)2 and molecular weight of CaO is 56 (equivalent weight = 28). Assume the lime and soda ash are 100 % pure.