NAMS 2002 Workshop - ICOM 2008

Drinking and Wastewater Applications III – 2
Wednesday July 16, 10:15 AM-10:45 AM, Maui
Coagulation-Ceramic Microfiltration Hybrid System Effectively Removes
Virus that is Difficult to Remove in Conventional Coagulation-
Sedimentation-Sand Filtration Process
N. Shirasaki, Hokkaido University, Sapporo, Japan
T. Matsushita (Speaker), Hokkaido University, Sapporo, Japan - taku-m@eng.hokudai.ac.jp
Y. Matsui, Hokkaido University, Sapporo, Japan
M. Kobuke, Hokkaido University, Sapporo, Japan
T. Urasaki, Hokkaido University, Sapporo, Japan
K. Ohno, Hokkaido University, Sapporo, Japan
INTRODUCTION Ceramic membranes have attracted attention in the field of
drinking water treatment in Japan. However, in general, ceramic membranes are
microfiltration (MF) devices, so their pore sizes are not small enough to exclude
particles with diameters less than tens of nanometers. Included among such
small particles are some of the pathogenic waterborne viruses. These viruses
cannot be excluded by ceramic membranes alone. To compensate for this
disadvantage, it was proposed that coagulation, which is usually employed to
destabilize and aggregate small particles and then to remove them under gravity,
be used in combination with ceramic MF. Our group has already reported the
usefulness of the coagulation- ceramic MF hybrid system for virus removal.
However, evaluation of treatment processes in terms of virus removal is
generally based on virus concentration quantified by plaque forming unit (PFU)
method; our previous report also evaluated the hybrid system by the method.
Judging from its measurement principle, the PFU method detects infectious virus
alone, but does not detect inactivated one. Therefore, quantification of virus in
the MF permeate by the PFU method might underestimate the potential risk of
virus, because a part of the virus is inactivated during the treatment process. If
the temporarily inactivated virus recovers its infectivity after the process, it might
pollute our drinking water. In this meaning, investigating removal of virus
including inactivated one as well as infectious one is very important for the
evaluation of treatment processes. Accordingly, the objectives of the present
study are to investigate the removal of virus regardless of its infectivity by using
polymerase chain reaction (PCR) method, and to compare the removals during
the coagulation-ceramic MF hybrid system and the conventional coagulationsedimentation-sand
filtration process for confirming superiority of the hybrid MF
system in virus removal.
MATERIALS AND METHODS (1) Virus used Bacteriophage MS2, whose
diameter is 23 nm, was used as a model virus. Virus was quantified by both the
PFU and PCR methods. The PFU method quantifies infectious virus, while the
PCR method quantifies total virus particles regardless of their infectivity.