Silt Density Index

Of the Silt Density Index (SDI) called (English for Schwemmstoffdichte index), and Fouling Index is a measure of the amount of particles in the water.

There is measured the time in which 500 ml of water (30 psi) penetrated at a pressure of 206.8 kPa by a membrane. After a certain time (typically 15 minutes ) the test is repeated. By the particles present in the water over time is reduced, the amount of water which flows through the membrane, the membrane is to be.

SDI is thus the average percent change per minute of the volumetric flow through a membrane, over a period of 15 minutes ( since the volume of 500 ml is set, it is possible instead of the flow rate directly with the time required for the membrane - penetration count ):

With

  • : First measurement for 500 ml (in seconds)
  • : Second measurement for 500 ml (in seconds) after minutes
  • : Time between the start of the first and start of the second measurement ( in minutes)

The difference between a measurement of filterable solids is the detected particle size. In the SDI measure particles are detected in the colloidal range. It can be used with a pore size of 0.45 micrometer membranes.

These values ​​are commonly used in the supply of reverse osmosis, because as an early prediction of clogging of the membranes used can be made. Values ​​usually <5 % / min.

Swell

  • What is SDI, simplesdi.com.
  • Membrane Technology
  • Wastewater treatment
  • Hydrology
Membrane fouling Particle (disambiguation)
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