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Hydrometallurgy

Thickener Water Recovery Calculator

The economic point of a thickener is often the clarified process water it returns to the overflow for reuse. This calculator estimates that water recovery from the dry solids rate, the feed wt% solids, and the underflow wt% solids: the feed and underflow slurry and liquid mass flows, the recovered water in t/h and m³/h, and the water recovery as a fraction of the feed water. It is a preliminary steady-state water-balance estimate only, assuming all solids report to the underflow. It is NOT a settling-rate or thickener-performance model, and it does not predict overflow clarity or water quality — it ignores overflow solids losses, entrainment, evaporation, bed inventory changes, rainfall, and seepage.

TypeInteractive engineering calculator

Calculator

t/h

dry solids basis

wt%

0–100 wt% solids by mass

wt%

must be higher than feed

kg/m³

liquor density

Result
Feed slurry mass flow500 t/h
Feed liquid mass flow400 t/h
Underflow slurry mass flow181.818 t/h
Underflow liquid mass flow81.8182 t/h
Recovered water mass flow318.182 t/h
Recovered water volume flow318.182 m³/h
Water recovery fraction79.5455 %
  • !Preliminary steady-state water-balance estimate only — assumes all solids report to the underflow.
  • !Does not model overflow solids losses, entrainment, evaporation, bed inventory changes, rainfall, seepage, settling performance, or process control.

Formulas

Feed slurry mass flow
ṁ_slurry,f = ṁ_solids / (feed% / 100)
Feed liquid mass flow
ṁ_liquid,f = ṁ_slurry,f − ṁ_solids
Underflow slurry mass flow
ṁ_slurry,u = ṁ_solids / (underflow% / 100)
Underflow liquid mass flow
ṁ_liquid,u = ṁ_slurry,u − ṁ_solids
Recovered water (mass)
W_rec = ṁ_liquid,f − ṁ_liquid,u
Water recovery fraction
recovery% = W_rec / ṁ_liquid,f × 100

Diagram

Thickener water recovery — recovered water = feed liquid − underflow liquiddilute feedrecovered water (overflow)dense underflowW_rec = W_feed − W_underflow

Worked example

A thickener treats 100 t/h dry solids. The feed is 20 wt% solids and the underflow is 55 wt% solids. Liquid density 1000 kg/m³.

  1. 01Feed slurry mass: 100 / 0.20 = 500.00 t/h, feed liquid = 400.00 t/h
  2. 02Underflow slurry mass: 100 / 0.55 = 181.82 t/h, underflow liquid = 81.82 t/h
  3. 03Recovered water: 400.00 − 81.82 = 318.18 t/h
  4. 04As a volume at 1000 kg/m³: 318.18 m³/h
  5. 05Water recovery: 318.18 / 400.00 × 100 = 79.55%
Result

Recovered water 318.18 t/h (≈ 318.18 m³/h), water recovery 79.55% of the feed water.

FAQ

Does this predict that the overflow will be clear?
No. It is a clean-water mass balance — the difference between the water in the feed and the water leaving in the underflow. Overflow clarity, entrainment, and water quality depend on settling performance and are not modelled.
Why does it assume all solids report to the underflow?
For a preliminary water balance it is the standard simplifying assumption. Real overflow carries a small solids loss, which this does not deduct — so the recovered-water estimate is slightly optimistic in that respect.
What drives the amount of water recovered?
The gap between feed and underflow percent solids. A dilute feed thickened to a dense underflow releases a large fraction of its water; a smaller gap recovers less. The dry solids rate scales the absolute flow.
Is this a thickener sizing or performance tool?
No. It estimates the recoverable process water for a given feed and underflow concentration. Settling rate, bed depth, and the achievable underflow density require settling testwork and vendor data.

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