Environmental Engineering Reference
In-Depth Information
problem(s). Thus, cocreation of innovation without the external interjection of real tech-
nological understanding could create products that induce feelings of safety but actually
could be harmful if the actual problems are not addressed.
An initial team obtained local water analyses from the municipality to understand what
was technically wrong with the water. We chose Mexico with the idea that their problem
was mostly pathogenic in origin, i.e., the classic “Montezuma's revenge.” In several meet-
ings with the local oficials, it took some coaxing to get the water test results. We had to
agree with both local and federal oficials that we would keep all information conidential
until we had their speciic permission to disclose what the real issues were.
We were shocked to learn that arsenic was at such high levels. Thus, despite the per-
ceived problem that pathogens were the real issue, the actual problem was levels of arsenic
far above the recommended exposure of standards in Mexico (25 parts per billion [ppb]
limit) and the United States (the US/WHO standard being 10 ppb). We set out to do our
own analysis on local water by taking our own samples and sending the samples both to
Mexican laboratories as well as laboratories in the United States. These tests eventually
conirmed the high level of arsenic in the water, and also established which laboratories
were most accurate and stable in their measurements.
We also visited the water treatment utility that the federal authorities had mandated
a few years earlier. The municipalities used wells for the source of water, and injected
chlorine into the water at the source via tanks of chlorine. Our tests conirmed that this
national effort largely took care of the pathogen problem, killing most bacteria and viruses.
However, the element-rich water remained, with arsenic being the most serious problem
(arsenic consumption has a direct and strong correlation with increased rates of cancer,
diabetes, brain function, and other health problems). As we developed the technical data-
base, we were told by many sources that arsenic was a dificult problem to solve, and to
do it economically was even more dificult. However, the database provided several pos-
sibilities, and we began to narrow down the choices for experimentation. Iterating with
our developing market application knowledge, we concentrated on adsorption-based sys-
tems because of the potential for low cost and 100% water yield (all the water being puri-
ied). Furthermore, such systems are compatible with the low water pressure situations
frequently encountered in Mexico, as well as rooftop cisterns that supply water during
water outages (the water from the well dries up at various times) requiring people to rely
on stored water.
To foster iteration and adaptation, we developed our alpha-beta-gamma prototype
process. In the alpha prototype (Figure 21.2), we set up materials experiments using test
columns in TWI's Cambridge, Massachusetts, laboratory. After comparison of multiple
potential materials technologies for the ilter media, we created more substantial test puri-
iers using standard water puriication media bed conigurations and sent them to our
rented home/laboratory in Mexico (these were termed the beta prototypes). Finally, after
testing for long periods in the real environment and several beta prototype iterations, we
built gamma prototypes that were closer to the actual commercial form of the product.
The form of the gamma prototype (Figure 21.3) relied on the factors from understanding
the market application. We learned that because of their pride in creating a healthy water
environment, the Mexican people generally did not want to hide the puriication system
below the sink; they wanted it to be visible to visitors. They also liked to uniquely decorate
their units, and wanted the unit to resemble a water cooler, as well as having hot- and cold-
water dispensing capability. We thus combined these desires with the actual puriication
media and TWI's irst product was born (TWI 1.0, Figure 21.4). It is a multistage, gravity-fed
system that removes arsenic, pathogens, and improves taste in a POD device.
