MICROFILT provide a SDI test kit is to assess the extent of suspended particulate (solids and colloidal) contamination in water & can be applied in process solutions also. A SLIT DENSITY INDEX (SDI), also referred to as Fouling Index. Although most systems have some pre-treatment these fine particles are responsible for the fouling of reverse osmosis membranes. In order to measure the degree of this fouling problem, a concept called Silt Density Index is used. High Index waters are measure of dirty, and contaminated, low index waters are clean and indicate suitability for the process. The SDI of the feed water is directly related to the filtration costs.