Fact Sheet AutoSDI Automated Silt Density Index Tester SDI Testing Made Easy If you thought performing a silt density index (SDI) test to predict membrane fouling potential was too tedious, costly and time consuming, welcome to AutoSDI from GE’s Water & Process Technologies! AutoSDI eliminates the need for stopwatches, graduated cylinders, calculators and tedious labor. In less than twenty minutes you will know 5, 10, and 15-minute SDI results as well as Plugging Factor. Fouling membranes and compromising water quality can be expensive. With the simple AutoSDI kit and a water source of 65 psi (4.5 bar) and at least 0.8 gpm (3.0 Lpm), membrane particulate fouling can be avoided and system performance optimized. The AutoSDI kit or Silt Density Index Testing System, as shown in Figure 1, includes the tester, carrying case, 12 VDC Power Supply, pressure guage, inline prefilter, SDI membrane filters (box of 100), and a user’s manual. What is the Silt Density Index Silt Density Index (SDI) testing quantifies the amount of particulate contamination in a water source. SDI is widely accepted for estimating the rate at which collodial and particulate fouling will occur in water purification systems–especially in applications using reverse osmosis (RO) membranes. Water sources often change their water quality and this test often needs to be done weekly or monthly. The AutoSDI Tester automatically calculates a relative value for the amount of suspended matter in feedwater streams. Measured values reflect the rate at which a 0.45-micron membrane filter will plug with particulate material when feedwater is flowing through it. The ASTM chose the 0.45 micron filter because it is more likely to clog from colloidal matter than from hard particles such as sand or scale. SDI testing is commonly used as an “early alert” to ensure that particulates in feedwater do not plug the micropores in RO membranes. How is SDI Calculated? The AutoSDI calculates SDI based upon the decay in flow rate during a 15-minute period across a new 0.45-micron filter installed in the built-in holding fixture. Flow rate measurement accuracy is ensured Find a contact near you by visiting www.ge.com/water and clicking on “Contact Us”. * Trademark of General Electric Company; may be registered in one or more countries. ©2011, General Electric Company. All rights reserved. FS1061EN.doc Feb-11

by automatically maintaining a constant 30 psi (2.07 bar) in the feed stream to the filter. In-Field flow calibration Flow rates are measured during the collection of 500 mL samples at the start of the test and after 5, 10, and 15 minutes. SDI units (percent decay per minute) represent the degree of plugging that may occur due to the feedwater stream particulate and colloidal levels. The 15-minute SDI (SDI 15) is defined by ASTM D 4189-95 as the interval required for accurate and standardized testing. The 5- and 10minute SDI values are only estimates of the 15minute value. No special tools or...