SDI - Using a silt density index measurement apparatus
Click the play button and see a video on how to use a EUROWATER SDI measuring apparatus. It is used to determine if a water source is suitable for reverse osmosis or nanofiltration treatment.
Measurements of SDI (Silt Density Index) are carried out for relatively clean water supplies (waterworks water) in order to determine the contents of colloids, thereby indicating how fast an NF or RO membrane will be clogged (fouling).
As colloidal materials vary considerably in form and character the measurements are only normative. The method is, however, considered the most applicable for predictions of the risks of fouling RO and NF membranes.
Example of how colloids and suspended solids can foul the filter of the measuring apparatus. Water with an SDI>5 (right) is unsuitable for RO or NF treatment.