Significance and Use 5.1 The SDI can serve as a useful indication of the quantity of particulate matter in water. 5.2 The SDI can be used to determine effectiveness of various processes such as filtration or clarification used to remove particulate matter. 5.3 The SDI has been empirically correlated with the fouling tendency of some water treatment equipment such as reverse osmosis devices. 5.4 The SDI may vary as a function of water temperature, and values obtained at different temperatures may not necessarily be comparable. 5.5 The SDI will vary with the membrane filter manufacturer. Thus, SDI values obtained with filters from different membrane manufacturers cannot be comparable.Scope 1.1 This test method covers the determination of the silt density index (SDI) of water. This test method can be used to indicate the quantity of particulate matter in water and is applicable to relatively low (<1.0 NTU) turbidity waters such as well water, filtered water, or clarified effluent samples. Since the size, shape, and nature of particulate matter in water may vary, this test method is not an absolute measurement of the quantity of particulate matter. 1.2 This test method is not applicable for reagent grade water Types I, II, and III of Specification D1193, or effluents from most reverse osmosis and ultrafiltration systems. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Go to ASTM D4189 at ASTM.org
