Analysing mass balance of viruses in a coagulation–ceramic microfiltration hybrid system by a combination of the polymerase chain reaction (PCR) method and the plaque forming units (PFU) method

Virus removal experiments using river water spiked with bacteriophages were conducted by an in-line coagulation–ceramic microfiltration hybrid system to investigate the effects of filtration flux (62.5 and 125 L/(m² × h)) and type of virus (Qβ and MS2) on virus removal. In addition, the mass balance of viruses through the hybrid system was analysed by quantifying the infectious and inactive viruses by a combination of the polymerase chain reaction (PCR) method and the plaque forming units (PFU) method. Even when the system was operated at high filtration flux (125 L/(m² × h)), high virus removal (>6 log) with short coagulation time (2.4 s) was successfully achieved by dosing polyaluminium chloride (PACl) at more than 1.08 mg-Al/L. Removal performances were different between Qβ and MS2, although their diameters are almost the same: greater virus removal was achieved for MS2 at PACl dosing of 0.54 mg-Al/L, and for Qβ at PACl dosing of more than 1.08 mg-Al/L. The combination of the PCR and PFU methods revealed that two phenomena, adsorption to/entrapment in aluminium floc and virucidal activity of PACl, partially account for the high virus removal in the coagulation–MF hybrid system.