SDI measurement is one of the best methods for
monitoring the performance of pretreatment equipment relative to the potential
for downstream membrane fouling.
The rate at which 500 mL of water passes
through a 0.45 micron filter at a pressure differential of 30 psi is measured
initially and after a time interval of 5, 10, or 15 minutes. The SDI index
is calculated as the ratio of these measured times subtracted from one,
multiplied by 100 and divided by the total time of the test in minutes.
Because the 0.45 micron filter is tight enough
to remove bacteria and most of their byproducts, the SDI test results tend to
better correlate with the performance of a membrane system than turbidity and
other non-membrane based analyses.
Copyright (c) 2012 CEA. All rights reserved.
February 11, 2013.