SDI

The Silt Density Index (SDI) is used to assess the tendency of a water to become dirty due to the content in colloids and suspended solids, and is a crucial parameter for verifying the proper functioning of a pretreatment system, in particular when it is placed upstream of a Reverse Osmosis.

Generally an acceptable SDI value is 3 but some require SDI values below 1.

The measurement of SDI is obtained by evaluating the decrease in flow through a filter, under the pressure of a constant pressure (ASME D 4189).