Millipore SDI Testing Kit

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Product #: 2195900

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The Silt Density Index (SDI) test is used to estimate particulate contamination in water and is a widely accepted method for assessing the potential for colloidal and particulate fouling in water purification systems. It is especially valuable for evaluating pretreatment performance in reverse osmosis (RO) and nanofiltration applications, helping determine the effectiveness of pretreatment processes such as coagulation, filtration and clarification.

The SDI test measures the rate at which a 0.45 µm filter clogs under a constant pressure of 30 psi. Lower SDI values indicate reduced membrane fouling potential. The decrease in flow rate therough the filter is converted into an SDI value between 1 and 100, with higher values signaling inadequate pretreatment or elevated suspended solids, which can result in more frequent membrane cleaning or replacement. An SDI test of less than 3 is generally acceptable for membrane operation without pre-treatment. An SDI of greater than 5 generally indicates the need for additional upstream filtration.