Preozonation Effects on Organic Foulants in a Coagulation-Ultrafiltration Membrane Process

The effect of integrating ozone ahead of coagulation, flocculation, and sedimentation (CFS) as pretreatment to ultrafiltration (UF) membranes was investigated at the bench scale for treatment of a surface water containing organic foulants. Ozone was applied before a CFS-UF process and compared with a CFS-UF condition without ozone as the control. While CFS alone reduced turbidity by 27%, CFS increased turbidity by 61% while applying ozone. When integrated with CFS and UF, however, ozone reduced filtrate true color by 40%, ultraviolet absorbance (UVA) at 254 nm by 10%, and specific UVA by 30%, relative to the control, indicating that while ozone had impaired turbidity removal during CFS pretreatment, it had improved removal of aromatic-rich organics. Fluorescent excitation-emission matrixes confirmed that humic acid-like and fulvic acid-like substances known to cause irreversible fouling were retained on the control membrane but were absent on the membrane when ozone was integrated with CFS pretreatment.