Brazil: Clean Water - Hold the Salt

{josquote}The membranes are thin synthetic skins, 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{/josquote}.

"The membranes would be effective for improving water quality in large cities supplied by springs that hold 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 desalinise ground water supplying small communities in the interior of Brazil's impoverished Northeast. Several government bodies 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 Programme, 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 organisations. There will be diagnostics of equipment that needs updating, 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 a major problem 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 Organisation 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 litres of desalinised 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 replacee the ones being imported, but it will be many more years until it is produced by industry," Kepler Borges França, coordinator of the laboratory 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 Programme, 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 Centre 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 bred. The rest is used in irrigating fields of saltweed, which absorbs salt from the soil and is a good food source for goats and birds.

Apart from desalination, the membranes have many different applications. Engineers at the UFRJ graduate school have used membranes to separate out 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 preservation 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 EMBRAPA's food research centre, 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 sulphates from sea water, which is injected into the wells to extract the oil. The presence of sulphates can cause problems in oil extraction by producing blockages.

(*Originally published by Latin American newspapers that are part of the Tierramérica network. Tierramérica is a specialised news service produced by IPS with the backing of the United Nations Development Programme and the United Nations Environment Programme.)

Source: IPS - Inter Press Service News Agency

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