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contaminants at the site of each project, but
finds them at only five to 10 percent of its
sites. When the team does encounter them,
they install additional treatment steps to
remove the harmful chemicals. In rare cases,
more complex and expensive technology, like
reverse osmosis, is required.
Reverse osmosis (RO) is what large water
bottling companies like Nestlé or Coca-Cola
use for their brands of bottled water. The
process is so effective at filtering out even
dissolved agents that the water it produces
is essentially pure. The final product is more
uniform both in chemical composition and
taste as a result, Malone says.
“Reverse osmosis is more of a ‘
one-size-fits-all’ solution and is great for creating a
consistent product,” Malone explains. Take
saltiness, for example. “Anything where the
salt concentration is more than 1,000 parts
per million (ppm) will start to have a bad
effect on taste, and anything above 2,000 to
3,000 ppm is when RO is the better technology choice,” he says.
There are several drawbacks to reverse
osmosis, however. For one, the upfront
costs and ongoing maintenance of an RO
Waters installed in the Dominican Republic
cost approximately $9,000, with annual
maintenance costs of about $1,800. A simi-
larly sized RO unit would have run close to
$15,000 and annual upkeep would have been
up to 2.5-times more costly. RO systems
also waste much more of the original water
source than ultrafiltration systems (50 to 60
percent versus five to 10 percent), and they
use about 10 times the amount of energy.
Ultrafiltration is a simpler technology,
but certainly not less safe; it is a tried and
tested process that is very cost-competitive
for Healing Waters, Malone says. “We like
it because it is really reliable, whereas with
other filtration systems, you might easily
end up with contaminated water if an opera-
tor makes a mistake.”
Malone says that local operators can eas-
ily be trained in how to clean ultrafiltration
units and “backwash” the filter membranes,
which ensures that they continue filtering
water at their optimal capacity. In all, this
takes 10 to 20 minutes each day. If the filters
are not maintained properly, the only conse-
quence is a slower output, not unsafe water.
By contrast, RO systems require anywhere
between two and four hours of maintenance
daily to ensure the systems’ numerous
filters are properly cleaned and performing
as intended. Generally, this has to be done
by a professional, because the risk of ruining
the filters and ending up with contaminated
water is high, says Malone.
ADAPTIVE USE
For Healing Waters, the benefits of making
its own equipment were immediately evident
when it launched the PowerPure in 2011. The
unit performed with good results, and the
charity was able to reduce its per-project
costs significantly. Some of the systems’
features still had to be sourced by outside
providers—namely, the ultrafiltration membranes, which cost about $300 each. But that
is a pretty small expense relative to what an
RO system would require, Malone says.
The one major limitation was that the
unit required a constant supply of electricity.
“The PowerPure has a pump that needs to be
plugged into a 120- or 240-volt power supply,
which definitely limits the places where you
can use it,” Malone explains—meaning that
the unit is well-suited for areas with fairly
reliable power.
But Healing Waters wanted to focus more
on remote communities, where there was
a higher need for clean water solutions and
fewer organizations doing the work. Since
power is less reliable in these areas, the organization set to work redesigning its system.
In 2012, it had developed a new model called
the GravityPure.
GravityPure uses the same ultrafiltration
process, but as the name suggests, it relies
on gravity rather than electricity to pull water
from its source through the filter. In order to
work, the water source must be elevated at
least seven feet above the system—a tank
mounted on a roof, for example—in order to
produce enough pressure to force the water
through the system’s filters.
Developing a gravity-based unit forced
the Healing Waters team to add a number
of flexible design features. For example, the
One ultrafiltration filter can
serve 500 people daily.
