1.1 ,This test method covers the determination of the modified fouling index (MFI) of water measured at constant pressure. This test can be used to indicate the fouling potential of reverse osmosis/nanofiltration (RO/NF) feed water due particulate matter and is applicable to low and high turbidity waters. 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.