Environmental Engineering Reference
In-Depth Information
should not be confused with a new technology or other such inventions; innovation in our
deinition is raised on the highest pedestal above invention and science, as only an inno-
vation has proceeded all the way to the marketplace through commercialization. Thus,
despite numerous research results on forward-looking concepts, progress in big water and
the last mile of water or POD has only been incremental. This incremental progress has
essentially been the insertion of slightly different technologies into existing business mod-
els. The production of fundamental or transformative innovation requires the simulta-
neous exploration of new market applications, business models, and technology. TWI was
formed with this challenge in mind: to create innovations by irst establishing a company
that employs a unique process to foster such innovation.
Since POD puriication is currently of the most interest to TWI, we note that many new
products are released every year in this sector, and most involve the same puriication
technology: activated carbon. Activated carbon has some puriication capability (mostly in
removing limited amounts of organic contaminants); however, the main feature is catalytic
reduction of residual chlorine disinfectants and thus changing the taste of water that was
puriied in centralized water plants using batch chlorine processes. Although of value in
developed countries, such products do not remove the wide range of potential contami-
nants in water, such as arsenic, luoride, and pathogens. Most of these new products use
new marketing or design techniques or a combination of both to garner a segment of
the “taste-oriented” marketplace, particularly in developed countries. Such products also
may beneit from the misconception that they actually purify water and remove additional
contaminants.
If we look for existing products and technology that can actually purify water in more
comprehensive ways at the POD, products that utilize reverse osmosis (RO) come to the
forefront. Essentially the universal solution from a puriication perspective, RO drives con-
ventional osmosis that occurs across a membrane in the opposite direction using energy
(through hydraulic pressure). Because there is a physical barrier (and not just pores),
very little can pass through the barrier except water, and, therefore, almost everything is
removed from the water.
However, there are many limitations to RO. While RO removes many harmful contami-
nants such as lead, it also removes beneicial minerals such as calcium and magnesium.
The process is maintenance intensive since membranes are sensitive to fouling and scaling,
frequently requiring pretreatment to improve lifetimes. In addition, they require signii-
cant energy to drive the process. Because of the previous considerations, reverse osmosis
systems are the most expensive solutions. Importantly, since there is a physical barrier,
puriication is slow and a large volume of valuable water is rejected (80%-90% is common
for home RO systems). Also note that the rejected water stream has a higher concentration
of the contaminant, and depending on the situation, its runoff may need to be treated or
contained to prevent ecological damage.
There are various materials processes that can add eficacy to activated carbon technol-
ogy but, in general, will not produce a universal product that can compete with RO. Thus,
very few products have appeared in this more advanced space, since such products typi-
cally would be more expensive than simple activated carbon solutions, and such products
often only perform targeted puriication of certain speciic substances. Consumers in devel-
oped countries do not want to pay an increased price for partial eficacy that they do not
need, and in developing countries, such solutions are risky because the consumer would
irst need to understand exactly what the technology problem in the water is and what
limited solution such technology is trying to address. Targeted solutions are most effective
when products are developed that address contaminants present in local water conditions.
