Generally the first membrane ...
Published by Govindasamy Manickam, GM at Adani Power Ltd.
Generally the first membrane (feed end membrane) fouls with high SDI. i.e. fouling with particles. The reject end membrane foul with scaling potential materials (Carbonate, silicate, phosphate, sulphate scales). Biofouling can happen at any location but high potential is towards reject end due to low flux.
Detailed study is required to diagnose the problem properly for prevention.