The DL/T 588-2015 standard specifies a method for measuring the water quality pollution index, which is suitable for the determination of the pollution index of reverse osmosis (RO) influent water with turbidity not greater than 1.0 NTU. The pollution index (also known as the silt density index SDI) is a technical indicator for measuring the content of pollutants such as particles, bacteria, colloids, etc. The measurement method includes passing the tested water sample through a microporous filter membrane with a diameter of 47mm and a pore size of 0.45 μm, and then filtrating it under a constant gauge pressure (207 kPa) to determine the time for the water sample to penetrate the membrane to calculate the pollution index value. This standard specifies the experimental conditions and calculation methods to ensure the accuracy and comparability of measurement results to evaluate the performance of reverse osmosis (RO) influent on the degree of pollution, and to provide a scientific basis for water quality assessment and treatment.