30 April 2018

Bricking arsenic from contaminated water

Arsenic contamination of drinking water is a serious problem for many people living in places are disparate as the Indian sub-continent, South America and the American mid-west. The problem affects mainly groundwater sources, and arises by dissolution of arsenic-containing rocks and ashes of volcaninc origin (and their weathering products), by oxidation of sulfur-containing minerals, and/or by mobilization of arsenic-retained iron oxides due to reductive dissolution and/or by arsenic desorption, which in turn is due to phosphate competition. These processes are in general naturally occurring, but human activities such as mining or mismanagement of groundwater resources can also be held responsible for arsenic pollution.

Chronic ingestion of arsenic at sub-toxic levels leads to a condition known as arsenicosis. The pathology of this disorder causes skin lesions such as dermatosis and keratosis, and ultimately skin, lung, bladder, kidney, and liver cancer, among other problems. The World Health Organization established guidelines on exposure and suggest that a total arsenic concentration of 10 micrograms per litre for arsenic in drinking water is the upper safe limit that balances likely levels in the developing world with a relatively safe rate that the body might clear this element once absorbed. Nevertheless, there are an estimated 226 million people exposed to much higher, and thus hazardous levels around the world.

In Argentina alone, around 4 million people, about one in ten of the population, are at risk of drinking groundwater containing natural, but nevertheless toxic, arsenic at concentrations exceeding the 10 micrograms per litre limit.

The decontamination of drinking water and well water is possible, but is generally rather costly and relies on technical equipment that is usually out of the reach of villages and other remote locations in the developing world, making thus necessary a continuous effort to develop new, more efficient and cheaper methods for arsenic removal. However, this decontamination will always generate a toxic waste product that itself must be contained to prevent arsenic leaching back into the environment and waterways.

Now, Jorge Martín Meichtry and Graciela Elizabeth De Seta of the Universidad Tecnológica Nacional, in Buenos Aires, Argentina, and their colleagues have devised a novel method of handling arsenic-containing waste in the form of a mortar formulation for the fabrication of materials that removes the arsenic from the environmental equation by locking it up into bricks made with Portland cement. The bricks can be safely used as construction hardcore or foundation materials or buried in a landfill with very little risk of the arsenic becoming soluble and leaching into soil and water. The team provides details of their work in the International Journal of Environment and Health.

De Seta, E.G., Reina, F.D., Mugrabi, F.I., Lan, L.E., Guerra, J.P., Laburu, A.P., Domingo, E.J. and Meichtry, J.M. (2018) ‘Safe disposal of solid wastes generated during arsenic removal in drinking water’, Int. J. Environment and Health, Vol. 9, No. 1, pp.50–65.

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