A water treatment plant uses chlorine gas to disinfect the w

A water treatment plant uses chlorine gas to disinfect the water before distribution. a) 5. The chlorine dosage is 1.5 mg/L, the chlorine demand is 1.2 mg/L. What is the residual concentration? b) If you are treating 550,000 gpd and plan to buy chlorine in 1-ton containers, how long will one container last?

Solution

(a) Chlorine dosage = Chlorine demand + Residual

So, Residual concentration = 1.5 -1.2 =0.3 mg/L

(b) 1 US ton = 907185 grams

550,000 gpd = 0.55 MGD

Chlorine used in lbs/day = (Chlorine dosage) (MGD flow) (8.34 lbs/gal) =lbs/day Cl₂

=(1.5 mg/L)(0.55 MGD)(8.34 lbs/gal)=6.88 lbs/day Chlorine

Time for one container = (1 ton)(2000 lbs/ton) / (6.88 lbs/day) = 291 days