Question

The solubility of sodium fluoride in water at 20 degrees C is 40,400 mg/L. City of Baton Rouge supplies 5mgd (million gallons per day) drinking water and the annual sodium fluoride usage is 126,000 kg. Based on the solubility data provided,

a. Check if the City of Baton Rouge, Louisiana is within the solubility limit for sodium fluoride

b. Does city of Baton Rouge, Louisiana need to make any changes to the amount of sodium fluoride usage to meet EPA requirement of 4 mg/L fluoride in drinking water.

Answer 1

solubility of NaF = 40.4 g/L

drinking water supply = 5 mgd = 5 * 10^6 * 3.7854 L per day = 1.8927 * 10^7 L per day

drinking water supply = 1.8927 * 10^7 *1/365 L per year = 5.1855 * 10^4 L per year

mass solution = 5.1855 * 10^4 * 40.4 g = 2.0949 * 10^6 g = 2.0949 * 10^3 Kg

Annually usage of Fluorine = 126000 kg and

Supplied F2 limit is = 2094.9 kg

The usage is higher than the solubility so we have to increase the amount of NaF so drinking water supply will be more.