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, normalised flow.
$ \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 ] $
Membrane rejection: normalised salt rejection, normalised permeate Feed/brine channel blockage/fouling: normalised differential pressure.
Calculators/spreadsheets
Dow http://www.dowwaterandprocess.com/en/resources/normalization_of_membrane_systems
Hydronautics http://membranes.com/index.php?pagename=rodata