Calculate polymer use in lb active per dry ton and the neat polymer feed needed for a target dose.
Polymer Dose (lb per dry ton)
Formula
Dry solids, lb/h = Feed gpm x 60 x 8.34 x %TS / 100 Active polymer, lb/h = Neat gph x density x %active / 100 Dose, lb/dry ton = Active polymer lb/h / (Dry solids lb/h / 2,000)
Inputs used
- Sludge feed rate (gpm)
- Sludge feed solids (%)
- Neat (as received) polymer feed (gal/h)
- Polymer active content (%)
- Neat polymer density (lb/gal)
Worked example (White River WRRF, fictional)
- Dry solids = 99 x 60 x 8.34 x 0.0294 = 1,456 lb/h = 0.728 dry tons/h
- Active polymer = 5.2 x 8.8 x 0.40 = 18.30 lb/h
- Dose = 18.30 / 0.728 = 25.1 lb/dry ton
Neat Polymer Feed for a Target Dose
Formula
Neat gph = (Dry tons/h x Target lb/dry ton) / (Density x %active / 100)
Inputs used
- Sludge feed rate (gpm)
- Sludge feed solids (%)
- Target dose (lb/dry ton)
- Polymer active content (%)
- Neat polymer density (lb/gal)
Worked example (White River WRRF, fictional)
- Active needed = 0.728 dry tons/h x 25 = 18.21 lb/h
- Neat feed = 18.21 / (8.8 x 0.40) = 5.17 gal/h
Tips
- Typical centrifuge doses for digested sludge are often 15 to 35 lb active/dry ton.
Results are estimates for operator use. Check units and inputs, and confirm decisions with plant data and procedures.