Water tools

Membrane rejection and log removal value

Rejection reads as a percentage; log removal reads as a count of nines. For pathogens and challenge tests the log form is the one regulators use.

Feed concentrationany unit

Permeate concentrationsame unit

Permeate result

Log removal value

5.89

Rejection

99.99987%

Nines

An LRV of 4 is 99.99% rejection; of 6, 99.9999%.

How it works

R e j = 1 - \frac{C_{P}}{C_{F}} L R V = \log_{10} \frac{C_{F}}{C_{P}} = - \log_{10} (1 - R e j)

(1)

where

$R e j$: rejection, fraction
$C_{F}, C_{P}$: feed and permeate concentration, any common unit
$L R V$: log removal value

When the permeate is below detection, the LRV is a lower bound computed with the detection limit. Rejection is not a step function at the pore rating: pore-size distribution, particle shape and charge all matter. Microfiltration should not be relied on for complete virus removal; ultrafiltration virus removal depends on the molecular weight cut-off. Adsorption and cake filtration add removal that is not credited.

Membrane rejection and log removal value

How it works

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