ASTM on Data Normalisation

ASTM D4516 - Standard Practice for Standardizing Reverse Osmosis Performance Data

Membrane performance (flux and salt passage) is affected by: water temperature, feed conductivity, and flux rate. If the operating arameters remain constant the system will perform fairly steadily over a long period of time. However, these operating conditions will eventually change. Normalisation is a technique that allows the user to standardise the data to a constant set of conditions (or to a reference), and may be used with SCADA for online diagnostics.

Flow or flux performance

Specific flux

$ \operatorname{Specific Flux} = \frac{Flux \times TCF}{NDP} $

Where: $ \operatorname{TCF} = e^{x} $

$ x = u\left( \frac{1}{T+273} - \frac{1}{298}\right ) $

NDP = Net Driving Pressure

$ NDP = P_{feed}-\Delta \pi-\frac{\Delta P}{n+1}-P_{permeate} $

$ P_{feed} = $ RO feed pressure

$ \Delta \pi = $ Osmotic Pressure

$ \Delta P = $ Feed/Brine Differential Pressure

$ n+1 = $ Number of membrane stages

$ P_{permeate} = $ Permeate back pressure

$ \pi = 0.006 \times $ Average feed / brine conductivity

$ \text {Average feed / brine conductivity} = \text {Conductivity of feed} \times \left [ \frac{\ln \left ( \frac{1}{1-Y} \right )}{Y} \right ] $

$ Y = \text {Recovery} = \frac{\text {Permeate flow}}{\text {Concentrate flow} + \text {Permeate flow}} $

Normalised Flow

$ \text {Normalised Permeate Flow} = \frac{\left ( NDPs \right ) \left ( TCFs \right )}{\left ( NDPa \right ) \left ( TCFa \right )} \text {Actual Flow} $

$ a = \text {actual} $
$ s = \text {standard} $

==Membrane rejection

Normalised Permeate Conductivity

$ \text {Normalised permeate conductivity} = \text {Permeate conductivity}\left ( \frac{\text {Actual permeate flow}}{\text {Standard permeate flow}} \right )\left ( \frac{\text {Standard feed/brine conductivity}}{\text {Actual feed/brine conductivity}} \right )\left ( TCF \right ) $

Feed/brine channel blockage/fouling

Normalised differential pressure

$ \text {Normalised} \hspace {2mm} \Delta P=\Delta P\left [ \frac{\left ( \text {Standard feed/brine flow} \right )^{1.5}}{\left (\text {Actual feed/brine flow} \right )^{1.5}} \right ]\left [\left ( T-25 \right )\left ( 0.017 \right ) +1 \right ] $

$ \text {Feed/brine flow}=\frac{\left ( \text {Feed flow} + \text {Concentrate flow} \right )}{2} $

Calculators/spreadsheets

Dow http://www.dowwaterandprocess.com/en/resources/normalization_of_membrane_systems

Hydronautics http://membranes.com/index.php?pagename=rodata