Question

The chemical composition of a water sample is given in the table below. The goal hardness is 80 mg/L as CaCO3 Water composition (mg/L): Ca2+ HCO3 15 SO42- Na* CO2 242 Mg2+ 56 (a) Convert the given ionic concentrations in mg/L to mg/L as CaCO3 (b) What is the total hardness, carbonate hardness and non-carbonate hardness? (C) What is the lime-soda dosage to soften the water to a hardness of 80 mg/L as CaCO3 (d) What is the annual cost of treating 0.15 m/s of the above water if the cost of lime and soda ash are $70 and $180 per Mg respectively? [Mg represents Mega-gram. 1 Mg = 100 g] [use 1000 L = 1 ml [Molecular weights (g) Ca = 40, 0 = 16, C = 12, H = 1, Mg = 24, Na=23] [Chemical composition of Lime is CaO and Soda-ash is Na2CO3]

Answer 1

Concentration Pn (my le) as cacos concentration (msle) x (Molecular Wit of) N Calo₂ Molecular wit Mwt Concentration | (m3/h) Concentration (mgle as calos) 96 x 100 = 245 13 14 x 100 = 62.5 3X100 2 9 1.304 :20 *100 = 45.45 396.721 58.334 191.55 (57. Cat2 lo 245 307.5 398.804 | Mgte | Net] Hos so 396.721 455.055 Total Hardness is due to ce+2 & Mg +2 | THE 307.5 mell as c2631 -- -

Total Alkalinity is due to coje a HCO3 A TA. 396.721 mylı as cenos TA >TH - CHITH : 307.5 mall as calos (CH: 307.5 mg/2 as coros) NCHED . (c). Required Hardnen. 80 mg/l as (CL03 Hardnen to be removed a 307.5-80 2 227.5 mile on Calos. Lime treatment will remove coz, Carbonate Handnem and magnesium salts. lime requireda (CO2) + (CH) + (18+2) - 45.45 + 307.5 + 62.5 ? 415.45 mein as callos Soda treatment will remove NCH. s sode required 2 O. Hardnen requireda 80 mg/l as Celos a time required a 415.45=80 2 335.45 mele as celos

S . X 3 - water .~ 0.15 m/see Volume in year e 0.1560x60x24 X365 ? 4730400 m3 2 473.04 *104 m2 : 2 473.04 X107 liters. Lime cost 2 $ 70 / Mga Lime required a 335.45 mg), as celo z 2 335.45 x 56 187.852 mez 187,852 mg / *.473.04x10² liters of water requireds 187.852 x 473.04810* mg 2 88861.51008 x 107 mg 2.888.615 Mg . Eerst Cost a 70% 888.615 $ $ 62,203.057

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