The importance of protecting aquifers from contaminated plumes

Do you know how many people depend directly on aquifers for drinking water? And the water used on irrigation for food production? No, right? The answer is that two billion people depend directly upon aquifers for drinking water, and 40 per cent of the world’s food is produced by irrigated agriculture that relies largely on groundwater according to The United Nations Environment Association.

Have you ever stopped a minute and thought about this? The real situation is that water stored in the ground beneath our feet is invisible and so its depletion or degradation due to contamination proceeds unnoticed for us.

So, what should we do about it? Over the years hundreds of studies have been carried out from all different angles to try and solve this problem, however, the industrial legacy and the current industrially dependent world where we live does not make it easy to get a solution. The realistic situation is that the world consumes beyond its resources generating non stop contamination and not taking enough decisions to stop them .

With this introduction, the scene is set up for the next step, what are we really doing to get a solution? Well, projects like ADVOCATE, NanoRem, SuRF-UK, CLARINET, etc. in the framework of Europe are looking for sustainable remediation practices, assessments, etc.

Technologies that range from natural attenuation to advanced oxidation processes such as wet air oxidation or supercritical CO2 extraction, etc., have been studied to date, however, this time, I would like to draw your attention to “Permeable Reactive Barriers (PRBs)” being one of the most promising remediation technologies to intercept and decontaminate plumes in the subsurface.

But, how do these barriers work? Why is it a promising technology? Johana Grajales and Franklin Obiri Nyarko, ADVOCATE’s fellows, are specialized in this topic and recently have published a detailed overview about it in the paper “An overview of permeable reactive barriers for in situ sustainable groundwater remediation”.

The PRB can be defined as a groundwater remediation technology that consists of introducing a wall of reactive material perpendicular to the groundwater flow path to intercept and treat the contaminants. The contaminants in the plume react with the media leading to either their transformation to less harmful compounds or fixation to the reactive materials. The challenge is to match the reactive material and the removal process to the contaminant.

In this paper, Johana and Franklin have carried out a detailed study of the state-of-art explaining the reactive media used so far and the mechanisms employed to transform or immobilize contaminants.

Although this is a promising low cost remediation technology there is still a lot to be done regarding the long-term performance of PRBs and improving their treatment of a broad spectrum of contaminants, and thereby expand their remit.

If you would like to know more about this paper, please click here:

Obiri-Nyarko F, Grajales-Mesa SJ, & Malina G (2014). An overview of permeable reactive barriers for in situ sustainable groundwater remediation. Chemosphere, 111, 243-59 PMID: 24997925

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