Features

• The FI value measurement unit FIU-20, including the filter holder KS-47 and the stand with the flow path switching cup, is unitized to enable accurate and simple measurement of the FI value (Fouling Index).
• Since the FI value is obtained from the ratio of the filtration rate between the two points t0 and t15 as follows, it is not affected by water temperature, filtration pressure, etc., and is useful for understanding the quality of the test water.
• The FI value is a pollution index that determines the degree of pollution of very small amounts of suspended and colloidal substances in water. In recent years, the measurement of FI value has become increasingly important because it is much more sensitive than turbidity measurement by scattered light. In this method, the test water is filtered using a 0.45 μm, 47 mm diameter membrane filter under constant pressure of 0.20 MPa (7).
• (1) The time taken to filter the first 500 mL (t0) was determined.
• (2) After continuous filtration for 15 minutes, determine the time (t0) required to filter 500 mL in the same manner. Use the following formula to determine the FI value:
• FI=(1-t0/t15)×100/15