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

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

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

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

Calculators/spreadsheets

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

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