Silt Density Index
Definition
A measure of the membrane fouling potential of feedwater, used for reverse osmosis rather than as a turbidity reading.
RO feed typically targets SDI below 5, distinct from NTU-based turbidity targets. It quantifies how quickly fine particulate will plug a membrane. It is the relevant solids metric where membranes, not tower surfaces, are the protected asset.
Related concepts
Part of The Blueprint of Water · 📏 measurement