Dewatered Cake Solids Calculator
How much cake will you haul, and how dirty is the filtrate going back to the head of the plant? Close the mass balance around your dewatering unit.
Dewatering Mass Balance
| Item | Value |
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How the calculation works
Formulas
Feed dry solids (lb/day) = flow (gal/day) × 8.34 × TS% ÷ 100
Cake dry solids (lb/day) = feed dry solids × capture% ÷ 100
Cake wet weight (lb/day) = cake dry solids ÷ (cake solids% ÷ 100)
Cake (wet tons/day) = cake wet weight ÷ 2000
Filtrate dry solids (lb/day) = feed dry solids − cake dry solids
Filtrate flow (gal/day) ≈ feed flow − cake wet volume (cake taken at ~8.34 lb/gal)
Filtrate TSS (mg/L) = filtrate dry solids (lb/day) × 106 ÷ (filtrate flow (gal/day) × 8.34)
Feed dry solids (lb/day) = flow (gal/day) × 8.34 × TS% ÷ 100
Cake dry solids (lb/day) = feed dry solids × capture% ÷ 100
Cake wet weight (lb/day) = cake dry solids ÷ (cake solids% ÷ 100)
Cake (wet tons/day) = cake wet weight ÷ 2000
Filtrate dry solids (lb/day) = feed dry solids − cake dry solids
Filtrate flow (gal/day) ≈ feed flow − cake wet volume (cake taken at ~8.34 lb/gal)
Filtrate TSS (mg/L) = filtrate dry solids (lb/day) × 106 ÷ (filtrate flow (gal/day) × 8.34)
Notes & limitations
The mass balance is exact arithmetic; the only approximation is filtrate flow (cake volume subtracted from feed at water density). Filtrate TSS is a check value — confirm with lab filtrate samples.
- Capture below ~90% means solids are escaping to the filtrate — check polymer dose, belt tension, and wash water before blaming the feed.
- Cake solids must exceed feed solids for the math to make sense; the tool rejects cake % at or below feed %.
- Filtrate returns to the head of the plant — high filtrate TSS is a recycle load that shows up as extra aeration and clarifier demand.
- Wet tons drive hauling cost. A single point of cake solids (e.g. 20% to 21%) cuts wet tons by roughly 5%.
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