A well water with a total hardness of 10.76 ppm is to be used for a pharmaceutical industry, which requires finished water hardness to be 3 ppm. An ion exchange resin is selected requiring 0.3 pounds of salt per kilo-grain of hardness removed to regenerate. What is the salt usage for each regeneration if the system regenerated every 10 days? What size resin tanks (diameter, height) would be required for a duplex system with no redundancy?

Assumptions:
Limit water loading rate to 8 gpm/sf
Resin capacity is 20,000 grains per cubic foot of resin
Grains per gallon: 17.1 = 1 mg/L
Water production is 1.0 mgd
Resin void is 50%