A team from the University of Huelva has designed a new technique to improve the quality of contaminated water from mining activity. The study has verified that the procedure allows the conditions for life thanks to tests carried out with a species that has verified the biological quality of the effluents due to their survival after the purification procedure.
Researchers from the Department of Earth Sciences and the Research Center on Natural Resources, Health and Environment of the University of Huelva together with the Coastal Research Center of the University of Atacama in Chile, have used the Asian clam as a bioindicator species of Mining water pollution. Experts have designed a debugging technique that lowers costs with respect to conventional systems, does not require energy consumption and its minimum maintenance cost. In addition, they have verified the effectiveness of the method at an ecological level demonstrating the possibility of the existence of life after cleaning the contaminated liquid.
For this, they have deposited the species in the different phases of the water purification process with a high concentration of toxic metals. In the last phase of the process where the purification has already been carried out, it has been shown that life is possible. Clams, being filtering organisms, act as sponges, capturing in their contaminating tissues, such as metals. Its scientific name is Corbicula fluminea and it is an invasive species present in Spain since the 1970s that was selected for the study due to its resistance capacity and adaptation to acidic environments.
The system developed by scientists is called ‘Alkaline dispersed substrate’ (DAS). It is a chemical purification technique where water flows by gravity. Through a mixture of pieces of wood with limestone sand a very permeable filter is created, which, when the acidic water passes, the sand dissolves, and when the pH dissolves, the metals precipitate and remain in the pieces of wood.
In this way, maintenance is minimal and much cheaper than that used for conventional treatment plants that use active mines. As indicated by the researcher at the University of Huelva Francisco Macías, author of the study: “The active mines have a budget and personnel for the maintenance of a conventional treatment plant, however when the installation is in disuse, it is necessary to have an alternative that reduces costs and maintenance ”.
The study entitled ‘Ecological improvement assessment of a passive remediation technology for acid mine drainage: Water quality biomonitoring using bivalves’ published in the international journal Chemosphere has had the University of Atacama, which has analyzed the water quality resulting from this new technique and their conditions for life through an experiment with Asian clams.
The work has consisted of depositing the species throughout the different stages of the new purification technique. First, in the original water of the mine, acid and contaminated, then in the treatment circuit and, finally, in the Odiel river. After all the biological and ecological studies carried out, it has been studied how many clams die and how the soft parts of the clam have absorbed metals.
After analyzing the results, they verified that the species dies immediately in acidic waters. However, at the time of chemical purification of water in the plant, the living conditions are high, approximately 95%, and do not suffer stress. Finally, when the water has run through the stream and reaches the Odiel, the probability of survival increases even more. That is why the work ensures that the technology developed allows conditions for life and also establishes that this species of clam can be a tool for biomonitoring pollutio.
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Source: Discover Foundation
Edition: majose.cadenas@sc.uhu.es