 |
|
|
Clean Water - Hold the Salt - in Brazil's Northeast |
|
By Mario Osava*
Brazil
is using semi-permeable membranes to eliminate toxins from water
in the impoverished northeast region. Promoters hope the technology
will be ready for local manufacturing within a few years.
RIO DE JANEIRO, Jan 29 (Tierramérica) - Thousands
of people in Brazil's semi-arid Northeast are slaking their thirst
thanks to a technology that is little used in Latin America: the
reverse-osmosis membrane, which desalinizes and purifies water.
A filter designed by Brazilian experts should be ready in two years.
The membranes are a sort of thin synthetic skin, made from different
materials -- generally plastic polymers. The process is known as
"reverse osmosis" because the semi-permeable membranes allow only
water to pass, leaving behind the impurities.
"The membranes would be effective for improving water quality in
large cities supplied by springs that receive a cocktail of contaminants,"
Renato Ferreira, project manager at the Environment Ministry's water
resources division, told Tierramérica. "The conventional water treatment
system does not eliminate heavy metals or agro-toxins, but the membranes
do."
For now, the membranes are being used to desalinize ground water
supplying small communities in the interior of the Northeast in
Brazil. Several government bodies have set up some 2,000 desalination
stations over the past decade, but most have been closed or are
operating precariously, because they are too small scale or the
operators lack training, said Ferreira.
The Fresh Water Program, launched in 2004 under his direction, is
aimed primarily at recuperating the equipment and ensuring its maintenance,
involving the local communities in management, and training technicians.
Executive groups have been created in each of the nine states involved,
with the participation of municipal governments, various agency
officials, and non-governmental organizations. There will be diagnostics
of equipment to update, and of new needs, with coordination of all
interested parties as a means to avoid the pitfalls suffered previously.
In the Northeast, where water shortages are dramatic as a result
of frequent droughts, subterranean water is an alternative, but
is generally very salty because of rocky soils.
Water in most wells has an average of about 3,000 parts per million
of salt, three times what the World Health Organization considers
apt for consumption, said Ferreira.
Throughout the semi-arid region there are some 100,000 wells drilled,
but 70 percent are already dry or the water they have is too briny.
That leaves approximately 30,000 usable wells, which could produce
an average of 4,000 liters of desalinized water per day each. Theoretically,
the total output would be enough to supply the 23 million local
residents.
Determining the capacity of each desalination plant, based on the
quantity and quality of each well, is indispensable. Some contain
a lot of iron and need prior chemical treatment to avoid damaging
the purification membranes. Others, with more calcium or magnesium,
require different water pressure for filtering, and equipment with
a specific number of membranes, which can range from three to nine,
Ferreira explained.
A simple three-membrane desalination unit costs about 7,000 dollars.
"It's not much, considering that it would supply some 800 people,"
commented the expert.
The membranes used in the process are imported, but researchers
at the federal universities of Campina Grande (UFCG) and Rio de
Janeiro (UFRJ) are developing models for a variety of water-purification
purposes, seeking technological independence and cost reduction.
"Within two years the UFCG's desalination laboratory will have a
membrane to substitute the ones being imported, but it will be many
more years until it is produced by industry," Kepler Borges França,
coordinator of the lab that is disseminating this technology in
the Northeast, told Tierramérica.
The laboratory is using ceramic as the base material for developing
its membranes. The imported membranes are polymers.
In the desalination process, according to the Fresh Water Program,
just half the water comes out clean. The other half is left with
double the concentration of salt and, initially, it was dumped,
contaminating the soil.
In response, the Semiarid Center of EMBRAPA, the government's agricultural
research agency, developed a system in which part of the salty wastewater
is used in fish farms where the tilapia rosa (Oreochromis sp) is
produced. The rest is used in irrigating fields of saltweed, which
absorbs salt from the soil and is good food for goats and birds.
Apart from desalination, the membranes have many different applications.
One achieved by engineers at the UFRJ graduate school is the separation
of aromas, already achieved in tropical fruits and coffee, improving
the taste of processed juices and instant coffee -- and giving Brazil
an edge in the respective international markets.
"The membranes allow the near total recovery of the aromas, which
in the orange, for example, include more than 200 components," professor
Cristiano Borges told Tierramérica.
The aromas are separated out through "pervaporation" (selective
evaporation of different components), using the membranes, explained
Lourdes Cabral, of EMPRAPA's food research center, which took part
in the coffee project. Obtaining the natural essence is vital for
the instant coffee industry, because Brazilian consumers otherwise
reject the project because it has less taste and aroma.
And there are membranes used in production of alcohol through fermentation,
with a great reduction in production costs, as well as others used
in the petroleum industry to filter substances like sulfates from
sea water, which is injected into the wells to extract the oil.
The presence of sulfates can cause problems in oil extraction by
producing blockages.
* Mario Osava is an IPS correspondent. |
