Abstract:
PAC/UF was investigated for removing M. aeruginosa cells and microcystins from natural waters
and its performance was compared with the conventional clarifi cation with PAC addition
(PAC+C/F/S). Ozonated and clarified waters from Tavira’s Water Treatment Plant were used. Both
processes achieved an absolute removal of chlorophyll-a, but greater turbidity and microcystins
(intra and extracellular) removals were reached by PAC/UF. With PAC/UF, 10 mg/L PAC resulted
in a cycle-averaged concentration of microcystins in the permeate (0.72 μg/L MC-LReq) below the
WHO guideline value, while the water quality obtained with 15 mg/L PAC+C/F/S was far beyond
that guideline value. However, the occurrence of cell lysis during UF (with subsequent release of
microcystins and UV254nm absorbing substances) and the preferential removal of high molar mass
compounds by coagulation yielded better UV254nm removals by PAC+C/F/S. Natural organic matter
showed a small impact onto microcystins removal, with greater effect of some algogenic compounds,
but especially of high concentrations of humic and tannic-like compounds.
