Forward osmosis organic fouling: Effects of organic loading, calcium and membrane orientation

► Organic fouling of FO membrane studied in FO and PRO modes using organic foulants from a RO reject. ► Minimal fouling in FO mode (up to 50-ppm TOC, even with 5 mM Ca2+ present in feed) ► Membrane fouling increased with TOC concentration in feed water in PRO mode. ► Severe fouling in PRO mode using feed containing 30 or 50 ppm TOC and 5 mM Ca2+. ► With 5 mM Ca2+, fouling layer resistance was slightly higher than membrane resistance.