cover 2006

of the basic element in water
treatment – the membranes that do
the actual work in filtering out
impurities.
“The membranes we use now are
far more efficient than earlier
versions,” Kasher says. “They have
good flux – water flows through
while salt doesn’t.We’ve also made
great strides in the engineering
aspects of reverse osmosis – how
much pressure to apply, how much
efficiency to expect. But up to now,
we’ve neglected the chemistry. We
don’t really understand how the
membrane itself works. Of course,
over the years, many different kinds
of membranes have been tested and
some are better than others.But we
haven’t studied how they work.
More importantly, we haven’t
studied how they could be
chemically designed to make them
better.”
Kasher describes the RO
membrane as a three-layer ply: the
working component is the “thin
film” which lies next to the salt
water; under that is a thicker layer
of porous material, then a stiff layer
for stability. “If we understood the
chemistry of the process, we could
design more efficient membranes,”
he explains.
One current problem is with
bacteria.”Bacteria collect on the
surface of the thin membrane,”
Kasher says. “As the bacteria layer
builds up, it clogs the membrane,
so gradually the membrane
becomes less permeable. Removing
the bacteria is costly, for several
reasons. First, the unit is taken out
of operation; second, it’s treated
with a chemical, often chlorine,
which might pose problems of its
own, such as generation of
carcinogenic agents from organic
substances. Repeated cleaning also
shortens the life of the membrane,
so it has to be replaced. Beyond all
that, labor costs are considerable.
“A specifically designed antimicrobial
peptide, which could bind
with the thin film, would represent
a serious breakthrough. What if
peptides could modify the surface
of the membrane so that it would –
by itself – prevent the growth of
bacteria? If an anti-microbial peptide
could target and kill the bacteria
before they built up, that would
represent a significant advance in
cost control.”
All of Kasher’s previous work
with peptides will come into play
on this new project, in which he and
a team of experienced researchers
will work on developing more
efficient membranes. “This is an
opportunity to take a big leap
forward in desalination technology,”
he says. “It’s an exciting project –
not just for Israel, but for every
thirsty country in the world.”
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