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Red Tilapia flourishes in waste saltwater

by the Fish Site Editor
27 April 2007, at 1:00am

BRAZIL - A village in Brazil's dry Northeast region is putting to the test a project that began with machine to desalinise the little water available, and has ended up creating food and income and promoting sustainable agriculture.

Caatinga Grande, founded in 1989 on land affected by agrarian reform near the town of So Jos do Serid, in the northeastern state of Rio Grande do Norte, aims to be a showcase for innovative technologies of the Programa gua Doce (fresh water programme), launched in 2004 by several state and non-governmental entities.

This modest village, with the Santa Rita church as a backdrop, has managed to scare off misery. Situated in the middle of Brazil's semiarid region, it was chosen to test a new technique for making use of waste from its well of saltwater, one of thousands in the Northeast.

The Caatinga Grande desalination station produces 10 litres of potable water daily for each of its 355 residents -- enough for their drinking and cooking needs.

But, "for each litre of potable water, we obtain one litre of water saturated with salts," Odilon Juvino de Arajo, a technician with the Brazilian agricultural research agency EMBRAPA, told Tierramrica.

And that salty wastewater contaminates soil and kills plants, explained resident Jos Anselmo Filho.

What to do with the wastewater became a source of disputes with neighbouring towns, until a new approach came from EMBRAPA, which was researching a possible solution in the nearby state of Pernambuco.

"We came to resolve an environmental problem" and ended up creating a "virtuous cycle" with the desalinator, said Arajo.

Less than 300 metres away from the village are three holding tanks that form part of that solution -- but they were initially seen with scepticism by the local population. "Since they have promised so many things, we have learned to distrust them. But now it's different. There are results," Netinha, a resident, tells Tierramrica as she points to the fish swimming in one of the tanks.

Potable water flows from the desalinator into a tank that supplies the community, while the wastewater is channelled to two other tanks where a resistant and tasty fish is raised: the red tilapia, a hybrid variety of the Oreochromis genus that adapts well to environments with high mineral content.

A third tank accumulates the used water from the two fish pools, which is rich in minerals and organic material -- and is also potentially a serious contaminant. But that liquid doesn't go to waste either. It is used to irrigate plots of saltbush (Atriplex nummularia), a forage crop of Australian origin that absorbs the salt and serves as food for the sheep and goats in the area.

The land where the tanks and the saltbush crops are located is set up with underground protection to prevent the salt from filtering into the deeper soils and groundwater.

"I had a hard time believing in this, but now the fish are fat and are going to provide a good yield," says Ccero Martins da Costa, one of the people responsible for the fish farm. He hopes to harvest 800 kilos of fish that the community will be able to sell, or eat it themselves.

"It's a source of income that didn't exist before," he says.

The tilapia take six months to reach maturity. But the start-up dates of the fish farm tanks are staggered by three months. This way, the community has four fish harvests per year.

According to Joo Bosco Senra, water resources secretary at the Environment Ministry, this technology could be implemented soon for many of the 2,000 desalinators installed on the wells in the "serto", the semiarid region in eastern Brazil, extending from the Jequitinhonha Valley in the southeastern state of Minas Gerais, through Bahia, Pernambuco, Sergipe, Alagoas and Rio Grande do Norte, to Cear.

"We are developing new materials to make it easier and cheaper to maintain the desalinators," Senra told Tierramrica.

The Programa gua Doce's financial backing comes from the Banco do Brasil Foundation. The cost of each unit installed is about 35,000 dollars, and includes repairs and updating of the desalinators, construction of the holding tanks, pumps to move the water, planting of saltbushes and technical assistance.

"The money is very well spent. It's about 50 cents (0.27 dollars) per person, per day, to ensure quality potable water, sanitation, food, income and a stimulus for goat and sheep production," says Foundation president Jacques de Oliveira Pena.

The Foundation will earmark 1.4 million dollars for expanding the initiative across Brazil's semiarid region. In total, the partners in the Programa gua Doce will provide 6.76 million dollars to replicate the endeavour in 22 communities in 11 states.

"The important thing is to have something concrete to show to the people of the serto," who will want to see results if they are to be convinced, says Pena.

the Fish Site Editor