Low-pressure membrane treatment processes are an emerging alternative to conventional
water clarification processes. Based on results obtained from pilot scale studies, several
full-scale treatment facilities have been recently built, and many other plants are currently
under construction or in their design phase. These facilities have been designed to
operate under conditions that result in minimal membrane fouling. Operating conditions,
such as permeate flux and cross flow velocity, have been studied by many researchers to
minimize particle deposition on membrane surface. However, there is limited
evidence demonstrating that these optimal conditions also correspond to maximum or at
least adequate rejection of microbial pathogens throughout the operating life of the
membrane system. Therefore, the effects of operating conditions on the microorganism
rejection need to be studied and determination of optimal condition for maximum
microorganism removal would be useful for designing or operating a full membrane
system. The purpose of this study was to perform bench scale experiments with
small units containing selected hollow fiber membranes to elucidate the role that
operating conditions (transmembrane pressure, permeate flux, cross flow velocity) play
on the rejection of microbial contaminants. Selected microorganisms are Bacillus subtilis
spores and MS2 phage.
A review of the literature reveals that removals observed for the common viral surrogate
MS2 phage in different studies could vary widely even when the membrane has the same
nominal pore size. For example, an MF membrane with a pore size of 0.2 um showed 0.2
log removal of MS2 with an outside/in operation mode but 1.2 log removal with an
inside/out mode. Additional studies using MF membranes with the same pore size of
0.2 um gave 1.9 log, <1 log, and 0.8 log removals of MS2. Consequently,
characterization of the membrane by its nominal pore size appears to be inadequate to
explain the mechanisms responsible for the transport of microbial contaminants through
microfiltration (MF) and ultrafiltration (UF) membranes. Therefore, one of the objectives
of this study was to investigate the mechanisms responsible for the transport of microbial
contaminants through MF and UF membranes. Membrane pore size distribution (PSD) is
considered an important factor to understand the mechanism of microorganism removal
by low-pressure membranes.
Includes 10 references, table, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1.9 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 9 |
| Published : | 11/01/2002 |
