A new technique to purify river waters contaminated by the mining activity

The Huelva province is at the moment the testing location of an idea that might rest the case when it comes to the mining activity that, notwithstanding its necessity, has contaminated the rivers by infiltration to such an extent that, in some cases, made the rivers’ natural colour vanish to make way to the hue of the minerals that reached the water.

The pioneering proposal is being tested in the Odiel basin and is evolving thanks to the LIFE ETAD project, co-financed by the European Union, with the participation of the company Sacyr Construcción, in the quality of engagement partner, the Consejería de Medio Ambiente, through Agencia de Medio Ambiente y Agua and the University of Huelva.

In this project, which counts on a 2.650.738 million Euros budget, participate, among others, the researcher of the University of Huelva, José Miguel Nieto, who tries to fight the acid waters with resource to scientific methods, “the result of the interaction of water with sulphides and mine waste, filled with acid and metals”. This blend ends up in the river basins contaminating the water, in such a way that sometimes it is noticeable to the naked eye.

The main rivers of the Huelva region, the Tinto and Odiel rivers feature this situation, and the experts managed to set in motion a system that allows turning these contaminated waters into clean waters, “in an ecological, low cost manner”.

The project aims at the conception and optimisation of the passive treatment process of acid mine drainage in a standard location in the Iberian Pyrite Belt, as well as the construction and activation of a passive treatment technology installation. The experts believe that this will contribute to achieve the goals of the National Hydrological Plan of the Tinto, Odiel and Piedras rivers, and likewise purified waters are to be achieved to serve as an irrigation resource for vineyards and citrus production, a feasible alternative in the affected areas.


“Neither electricity nor reagents"

The promoters of the initiative believe that a strong case for the system is that it does not alter the environment “because it does not resort neither to electricity nor to reagents to operate”, and even the installation has been projected “in such a way that, by means of electricity, the water to flow from a part of the system to the other and the cost of consumables to be minimum”. The experts successfully tested in laboratory a system based in small grains of limestone and calcium carbonate to be used as reactive substrate”.

After the success inside the lab, it is time to go out to the field. Presently, the treatment station is being dimensioned so that Sacyr can proceed with the works in the upper part of the Odiel basin in 2015.

The results previewed state the capacity of full scale passive technologies as feasible treatment of acid mine drainage, the improvement of the water quality in the area and the resource to technologies that would solve a serious environmental problem that affects degraded waters.

At the moment, testing will take place in the mining sites of Andalucía, although the Life Etad project aims at presenting itself as a reference pilot project for other areas affected by similar problems in the European continent.

The system is so simple that it only consists on rising the water PH levels close to 3 - the level to be found in contaminated rivers – to levels above 6, a level in which the dissolved metals precipitate. For this to happen, reactive filters will be used so the water can flow by means of the gravity effect.

Nieto highlighted that the background of this idea rests in the 90’s with passive treatments used for contaminated waters derived from the coal extraction in mines in the USA, Canada and England. Nevertheless, the tests revealed little efficacy, since the filters collapsed and lost effectiveness. The tests performed in the Odiel river, resolved that problem.

The scope of the experts’ action will be vast, due to the intense mining activity performed in the Iberian Pyrite Belt, which resulted in abandoned mines and mining waste in slag heaps, sludge deposits, open air pits, etc. These degraded areas are the main contamination source of both surface and ground waters in the Odiel basin, due to the acid drainage they generate. The acid mine drainage consist of water that undergoes an alteration of its PH to acid levels, which is exactly the problem that is to be solved.



In the entire Iberian Pyrite Belt.

The work set in motion by the leading experts might be applied in the entire Iberian Pyrite Belt, a concentration of massive sulphorides that stretches along a great part of the southern Iberian Peninsula. It is about 250 kilometres long and between 30 and 50 large, from Alcácer do sal (Portugal) to the province of Seville.

It is estimated to have lodged the greatest stock of non-ferrous metals in the world. Experts estimate that since the last 5.000 years, 2.000 million tons of mineral have been explored and around 400 are still left.    

It counts on explorations in Canal-caveira, Lousal, Aljustrel, Neves-Corvo and São Domingos (Portugal) and in the province of Huelva counts with Las Herrerías, Tharsis, La Joya, El Buitrón, Minas de Riotinto, San Miguel, Lomero-Poyatos, Cueva de la Mora, Cala, Castillo, Teuler, Mina de Aguas Teñidas and  Las Cruces, some of which penetrate in Seville soil.

The experts are presently registering the patent, but their work has already drawn the attention of South American countries, of South Africa and of Japan and it states its efficacy in the improvement of the water quality in the area directly affected by the mining activity.


Source: El diario.es

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