Environmental Engineering Reference
In-Depth Information
In fact, we already know the answer to that. Even the best membranes can only go so far
in reducing the energy needed to separate water from salt. The fundamental entropy term
remains unchanged however the hardware is improved, and that limits energy improve-
ments to the core process to around 40% of current best practice in RO. Building a better
RO membrane is analogous to building an extremely eficient crane to lift a 100-ton weight.
After the friction and motor ineficiencies are whittled away, the crane still has to lift that
100 tons. Given a modest 40% ceiling to improved performance, all of the ancillary ques-
tions we have walked through immediately come to the fore.
A more modest nano breakthrough in membranes makes the case. NanoH2O, with its
zeolite nanoparticle-impregnated membranes, has worked for years to penetrate the mar-
ket with what they claim is a solid improvement in performance at a slight price premium.
1
The company has raised more than $110 million from investors since 2007 without achiev-
ing proitability, this in a membrane market whose total annual value, never mind the
fraction the company might reasonably address, is only 15× that raise.
If membrane performance was the key element in RO, buyers would have locked to an
improved membrane years ago. NanoH2O continues to make inroads into the market,
and may one day win versus incumbents such as Dow, who according to one expert we
spoke to has not signiicantly modiied the design of their membrane for 30 years. But it is
already too late for NanoH2O to make a fast or huge proit for its investors. It is operating
in a commodity market and offering what amounts to incremental improvement to one
component of a complex system. All RO membrane manufactures are doomed to do the
same, given the fundamental physical limitations of the technology. Anyone who claims
to have a “revolutionary” RO membrane either does not understand the physics or has
devised what would be a real breakthrough: a cheap well-performing membrane that can
actually withstand inexpensive cleaning with chlorine.
10.2 Looking for Nano Treatment Breakthroughs beyond Membranes
Nano treatment is not limited to membranes. We recently spoke to Raphael Semiat of
Technion Israel Institute of Technology. Professor Semiat is bullish on nanoparticles as
water treatment to remove phosphates and contaminants such as selenates, or as high sur-
face area catalysts for advanced oxidation reactions with hydrogen peroxide. He acknowl-
edges, however, that the particles must be effectively iltered out before release to the
environment or human consumption, and that is a major sticking point before the technol-
ogy can be commercialized. Cost is also a consideration: to be practical, the particles must
be reusable, meaning they must be collected, reactivated, and redeployed without losing
their identity as individual particles.
Such strategies cannot be dismissed out of hand, but the inherent conlict between the
particles' chief advantage, high surface area and small size, and the imperative to collect
and remove them, suggests a relatively narrow window for success. Particles must be able
to aggregate without becoming inextricably bound, and must be free loating but easily
recaptured. Any solution that meets these conlicting criteria will still be subject to sig-
niicant regulatory review. Even compromises that bind particles to a substrate will face
skeptical regulators who will wonder what happens as the system degrades. The large
volumes of material needed for such systems will also immediately face developers with
the prospect of rapidly scaling up production.
