Two possible mechanisms have been proposed for coliphage
removal by the secondary treatment process (Kim and Unno, 1996).
The first mechanism involves adsorption of coliphage onto the
biological floc, while the second mechanism involves the removal of
coliphage through predation by other microbes such as protozoa
and metazoans. It is known that the attachment of poliovirus to
silica beads at pH 7 was 2–3 times higher than that of MS-2
bacteriophage (Bales et al., 1993)