Optimization of inline coagulation in integrated membrane systems: A study of FeCl3

This research investigated the effect of different process conditions (pH, G, Gt and coagulant dose) on inline coagulation pre-treatment of ultrafiltration (UF) with FeCl3. Delft canal water was coagulated with FeCl3 and filtered through a 0.1 µm PVDF filter in an Amicon unstirred cell. Filtration was performed in dead-end mode at a constant pressure of 0.1 MPa and at 20°C. Membrane fouling was quantified by calculating the modified fouling index (MFI) of the coagulated solutions. For coagulation with FeCl3, results showed that at higher coagulant dose (>10 mg Fe3+/L), the effect of flocculation time on MFI becomes negligible such that MFI is almost constant for 15 mg Fe3+/L for flocculation times ranging from 0 to 60 min. It was also observed that a relatively high dose (5 mg Fe3+/l) and long flocculation time (60 min) can compensate for the adverse effect of low pH on MFI. While proper flocculation can be designed and achieved prior to membrane filtration, Gt and retention times within the pipes and mem...