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Camille Rose A. Ignacio of this paper wrote on March 24 that the day
may come when water would be dearer than crude oil.
Earlier, on March 22, World Water Day, Ban Ki
Moon, the secretary-general of the United Nations, declared that
“…today, fresh water resources are stretched thin. Population
growth will make the problem worse. So will climate change. As the
global economy grows, so will its thirst.”
Both are right—up to a point. It’s true that
because of overuse and pollution the traditional sources of fresh
water—aquifers, rivers, lakes, dams—might not be enough to meet
the ever increasing needs of agriculture, industry and households.
Already, the Philippines is experiencing water
stress. The latest symptom was the outbreak of typhoid fever in two
provinces. Both epidemics were traced to contaminated water.
This said, there’s a major source of water
that remains to be tapped—if not for crop irrigation—at least
for drinking and cooking. This is the sea.
I hasten to add that we should continue to be
miserly in our use of water. Fresh water is getting scarcer. More
efficient methods of irrigation have to be found. Water sources
should be kept pristine. The price of water must be revised upward.
Unless I completely misread the reports of the
International Panel on Climate Change (IPCC), global warming will
not shut down the water cycle. Rain will continue to fall, not
perhaps in the usual places and seasons, but the oceans will
continue to be replenished.
The technologies to remove salt from seawater
are well known. They are distillation and reverse osmosis. The first
involves boiling seawater and then condensing the vapors. The second
works by pumping seawater at high pressure through a filter or a
membrane to separate the salt from the water. Both are
energy-intensive, expensive to maintain, and produce large amounts
of salt that are not easy to get rid of.
There’s a third method. It’s called
low-temperature thermal desalination (LTTD). The basic idea is
simple. Water at the surface of the ocean in the tropics is warm,
averaging between 26° and 30°C. However, at 350 meters below the
surface the temperature is about 13°C. Surface water is pumped into
a vacuum where the low pressure causes some of the water to
vaporize. In another chamber, cold water drawn from the depths
condenses the vapor into fresh water. This is how nature makes rain.
LTTD is something of a serendipitous technology.
It derives from an idea proposed in 1881 by the French physicist,
Jacques d’ Arsonval, that was revived when the need for a cheaper
energy source became pressing. However, converting ocean thermal
energy into electricity was not economic even at $80 per barrel of
crude oil.
This did not stop the US and Japan from
experimenting with the technology for proof of concept. However,
LTTD, the offshoot, has proved to be commercially viable. A thermal
desalination plant had been operating in Italy since the early
1990s. LLTD did not win any adherents—except in India.
Over a year ago, the National Institute of Ocean
Technology of India (NIOT) built such a plant on the island of
Kavaratti. It produced about 100,000 liters of fresh water a day but
it used 30 percent more energy per unit of water than a reverse
osmosis plant did. NIOT’s engineers thought that by scaling up the
technology a 100-fold the cost may be brought down.
To test this hypothesis, a one-million-liter per
day plant was built on a floating barge off the cost of Chennai. A
60-day trial proved their point. NIOT today is inviting investors to
build a 10-million-liter per day facility that would bring down the
cost to about $1 per 1,000 liters. This is 25-percent cheaper than
reverse osmosis.
Some experts are skeptical but they agree that a
scaled-up project is worth pursuing.
Since the Kavaratti plant became operational,
NIOT had been able to produce enough fresh water two hours a day for
11,000 islanders.
An important side benefit was a 50-percent drop
in diarrhea incidence. The island’s septic tanks have polluted the
shallow water table.
The Chennai plant is the bigger economic test.
BEFESA, a Spanish water company, is building nearby a
100-million-liter reverse osmosis plant.
NIOT officials are not fazed. Given the acute
need for water in many parts of India, their experiments are being
watched eagerly.
Our own water authorities—if they are not yet
aware of the experiments on Kavaratti and Chennai—might want to
look into low-temperature thermal desalination technology for
possible application in the Philippines.
My take is there will be no water shortage—it
will just become more expensive but it will not be as costly as
gasoline or diesel fuel.
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