Silt Density Index (SDI): is a common parameter applied for the fouling potential of feed
water for Reverse Osmosis and Nanofiltration membranes. It is based on the
measurement of plugging a membrane filter having 0.45 m at a pressure of 210 kPa.
Even though it has been reported several deficiencies about the use of this parameter, it
is still used in operation plants as fouling indicator.