
OPERATORS MANUAL
ORION II
Orion II 500-10000 Operators
Page 89 of 95
Manual Part no: DOMAON0100 Issue A
April 2008
Rejection rates vary with the nature of different types of impurities, thus particles, colloids, highly
ionised salts and high molecular weight components are highly rejected by RO membranes.
Conversely, low molecular weight organics, acids, alkalis and gasses, particularly carbon dioxide are
poorly rejected.
A rejection rate of 99% means that that only 1% of the impurities will pass through the membrane.
A 99% rejection membrane would therefore produce a permeate quality 5μS/cm on a feed water
supply of 500μS/cm. However by running membranes at high recovery levels with concentrate
recirculation results in considerably higher conductivities being fed to the membranes. This in turn
results in higher product water conductivities of 10 -
20μS/cm and an overall system rejection of 96 –
98%.