Removal of water-borne microorganisms in floating media filter-microfiltration system for water treatment

Floating plastic media pre-filter (PP) in combination with microfiltration membrane (MF) was applied to the removal of water-borne microorganism from surface water. The system was operated with and without coagulant addition. Jar-test results suggested that alum and polyaluminum chloride could effectively remove turbidity, fecal coliforms (FC) and algae at their optimum doses. Nevertheless, none of those coagulants could accomplish high coliphage (CP) removal. Microorganism removal in the system was increasing along with time in the PP unit operated at 5-m3/m2/h filtration rate but opposite trend was observed at higher filtration rates (10–15 m3/m2/h). Different coagulant types and filtration rates employed in the PP unit also affected microorganism removal in MF unit. The operation of PP unit at a filtration rate of 15 m3/m2/h and MF unit at a filtration rate of 0.6 m3/m2/d could achieve satisfactory turbidity and overall microorganism removal.