Water tools

RO concentrate flow and concentration from recovery and rejection

Every RO plant makes a second product: the concentrate. Its volume follows from recovery and its strength from the mass balance. Both drive the disposal cost.

Permeate flow requiredm³/d

Recovery%RO typically 50 to 85% on brackish water; 80% is a common practical limit.

Rejection%Per constituent: 85 to 99.5% for RO.

Feed concentrationmg/LTDS or any constituent with its own rejection.

Concentrate flow

444m³/d

Feed flow

4,444m³/d

Concentrate concentration

9,100mg/L

Permeate concentration

100.0mg/L

Concentration factor

9.10

Concentrate as share of feed

10%

RO concentrate is typically 15 to 50% of feed, nanofiltration 10 to 30%.

How it works

Flows from the recovery, permeate quality from the rejection, and the concentrate from the mass balance:

Q_{C} = Q_{P} \frac{1 - r}{r} Q_{F} = Q_{P} + Q_{C} C_{P} = C_{F} (1 - R e j)

(1)

C_{C} = \frac{Q_{F} C_{F} - Q_{P} C_{P}}{Q_{C}} = C_{F} \frac{1 - r (1 - R e j)}{1 - r}

(2)

where

$Q_{P}, Q_{C}, Q_{F}$: permeate, concentrate and feed flow, m³/d
$r$: recovery, fraction
$C_{F}, C_{P}, C_{C}$: feed, permeate and concentrate concentration, mg/L
$R e j$: rejection of the constituent, fraction

Apply per constituent with its own rejection: barium, strontium, silica and sulfate are what disposal and scaling care about. The concentrate is high in dissolved solids, low in suspended solids, often anaerobic, and is classed as an industrial waste; cleaning solutions are a second, smaller stream usually blended into it.

RO concentrate flow and concentration from recovery and rejection

How it works

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