Fluoride Feed Dose (Available Fluoride Ion)
The pounds-per-day of a fluoridation chemical to hit a target fluoride level -- the pounds formula (net dose x flow MGD x 8.34) with the two corrections the generic chemical-feed tile omits: divide by the AVAILABLE FLUORIDE ION (AFI) fraction and the commercial strength, and first SUBTRACT the raw background fluoride the water already carries. AFI is fixed per chemical: fluorosilicic acid (H2SiF6) 0.792, sodium fluoride (NaF) 0.452, sodium fluorosilicate (Na2SiF6) 0.607. Feeding a net 0.6 mg/L (0.7 target minus 0.1 raw) into 2 MGD with 25% fluorosilicic acid = 0.6 x 2 x 8.34 / (0.792 x 0.25) = 50.55 lb/day of acid, carrying 10.0 lb/day of fluoride ion. US PHS target 0.7 mg/L. A feed-setpoint aid; the daily lab checks, the SDWA maximum, the exact product assay, and the state fluoridation program govern.
Formula and source
net_dose = target_dose_mg_l - raw_fluoride_mg_l; pure_fluoride_lb_day = net_dose x flow_mgd x 8.34; feed_lb_day = pure_fluoride_lb_day / (afi_fraction x purity_fraction). AFI: fluorosilicic acid 0.792, sodium fluoride 0.452, sodium fluorosilicate 0.607.
Water-fluoridation feed calculation (CDC Water Fluoridation / AWWA practice), the available-fluoride-ion pounds formula, by name; the state fluoridation program, the SDWA maximum, and the product assay govern.
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