Dechlorination Chemical Dose

Reagent dose (mg/L) = a stoichiometric ratio x the chlorine residual to remove; feed (lb/day) = dose x flow (MGD) x 8.34 / purity. The ratio (mg reagent per mg Cl2) is reagent-specific and editable: ~0.9-1.0 for SO2, 1.34 sodium metabisulfite, 1.46 sodium bisulfite, 1.77 sodium sulfite, ~0.56 sodium thiosulfate. Removing a 2.0 mg/L residual from 5 MGD with sodium bisulfite is a 2.92 mg/L dose and 121.8 lb/day of 100% product; less-pure product needs more. Sulfur dechlor consumes dissolved oxygen and depresses pH, so an over-dose has its own permit cost -- dose to just neutralize, and confirm a near-zero residual downstream of mixing. A dosing estimate; the discharge permit, the reagent assay, and the state primacy agency govern.

reagent_dose_mg_l = stoich_ratio x chlorine_residual_mg_l; feed_lb_day = reagent_dose_mg_l x flow_mgd x 8.34 / (purity_pct/100). Ratio (mg reagent/mg Cl2): SO2 ~0.9-1.0, metabisulfite 1.34, bisulfite 1.46, sulfite 1.77, thiosulfate ~0.56.

Dechlorination stoichiometry with the pounds formula (Standard Methods / wastewater-operations practice), by name; the discharge permit, the reagent assay, and the state primacy agency govern.

The reagent-to-chlorine stoichiometry and the pounds formula are public (8.34 lb/gal water); the residual, flow, reagent ratio, and purity come from the process, the permit, and the product.

Estimate. AHJ and licensed professional govern.

Field names used by the API: chlorine_residual_mg_l, flow_mgd, stoich_ratio, purity_pct, reagent_dose_mg_l, feed_lb_day

• Stoichiometry + pounds formula reagent dose = ratio x Cl2 residual; feed = dose x MGD x 8.34 / purity; ratio SO2 ~0.9-1.0 / metabisulfite 1.34 / bisulfite 1.46 / sulfite 1.77 / thiosulfate ~0.56wastewater-operations practice
• Do not over-dose sulfite consumes dissolved oxygen and lowers pH; dose to just neutralize and confirm a near-zero residual downstream; the permit and primacy agency governNPDES permit / Standard Methods