Institute IMDEA Water, Rey Juan Carlos University and the Center for New Water Technologies Foundation are studying the application of horizontal reactive permeable barriers in the recharge of aquifers with reclaimed wastewater as a possible measure to combat water scarcity.

María Leal Meca (Universidad Rey Juan Carlos and IMDEA Agua)

In Spain there are problems of water scarcity that lead to major territorial, political and, above all, social disputes (MMA, 2000). For this reason, more and more organizations, institutions, managers, etc. are asking themselves the question: how can we face a scenario of increasing water scarcity?

In the scientific-technological field, several solutions have been proposed, with very different economic and environmental costs. But perhaps one of the most important in recent years is the reuse or reclamation of wastewater. In this way, what was initially a waste product is converted into a valuable new resource. Hochstrat et al. (2005) estimated the potential reuse capacity in Spain at more than 1200 Mm3/year.

With this starting point and under the protection of R.D. 1620/2007 (B.O.E., 2007), the regeneration of wastewater through reactive permeable barriers for aquifer recharge is one of the lines of research currently under development at IMDEA Agua, in collaboration with researchers from the Universidad Rey Juan Carlos and the Fundación Centro de las Nuevas Tecnologías del Agua (CENTA).

Permeable Reactive Barriers (PRB) are in situ treatment zones formed by reactive materials that transform or immobilize contaminants when water flows through them (US-EPA, 1998 & 1999; Ott, 2000). This technology has been applied to a broad spectrum of contaminants (Simon and Meggyes, 2000; Gibert et al, 2003; Tratnyek et al, 2003; Bozicco et al, 2004; di Natale et al, 2008), demonstrating its effectiveness in the decontamination of both organic (e.g. organochlorines) and inorganic compounds (e.g. heavy metals, nitrates and phosphates).

It is considered one of the most viable alternatives due to its cost/results ratio in the decontamination and regeneration “in situ” of both soils and groundwater. Moreover, on the one hand, it is an environmentally sustainable solution because it reduces pollution and has low energy consumption, and on the other hand, it is economically viable even for small populations where resources are much more limited.

Traditionally, barriers have been installed vertically in the ground to intercept the contaminant plume (Figure 1). But why not change the traditional vertical installation for a horizontal one (as a reactive bed) and instead of pollutant plumes have treated wastewater pass through it? Figure 1. Schematic of a Reactive Permeable Barrier (US-EPA, 1998)

The aforementioned research team is studying the feasibility of installing a horizontal PRB composed of different reactive materials at the bottom of aquifer recharge ponds. Thus, as the treated wastewater passes first through the barrier and then through the soil, its pollutant load decreases, thus reaching an adequate quality. This is made possible mainly by adsorption, surface complex formation, ion exchange and co-precipitation processes. Thus, through this treatment and with these physical-chemical processes, the objective set out in the Water Framework Directive (D.O.C.E., 2000) of achieving good ecological and chemical status of all bodies of water by not introducing polluting substances into the aquifer would be met.

Bibliographic references

B.O.E. (2007). Royal Decree 1620/2007, of December 7, 2007, which establishes the legal regime for the reuse of treated water. Official State Gazette, 294 (December 8, 2007): 50639-50661.

Bolzicco, J., C. Ayora, T. Rötting, J. Carrera. (2004). Performance of the Aznalcóllar permeable reactive barrier. A: International Mine Water Association. IMWA: 287-299.

D.O.C.E. (2000). Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy. Official Journal of the European Communities, 372 (December 22, 2000): 1 – 72.

Di Natale, F.; Di Natale, M.; Greco, R.; Lancia, A.; Laudante, C.; Musmarra, D. (2008). Groundwater protection from cadmium contamination by permeable reactive barriers. Journal of Hazardous Materials,160: 428-434.

Gibert O., de Pablo J., Cortina J.L.; Ayora, C. 2003. Evaluation of municipal compost/limestone/iorn mixtures as filling material for permeable reactive barriers for in-situ acid mine drainage treatment. The Journal of Chemical Technology and Biotechnology, 78: 489-496.

Hochstrat, R.; Wintgens, T.; Melin, T.; Jeffrey, P. (2005). Wastewater reclamation and reuse in Europe: a model-based potential estimation. Water Supply, 5 (1): 67-75.

MMA (2000). White Paper on Water in Spain. Ministry of the Environment, Madrid.

Ott, N. (2000). Permeable reactive barriers for inorganics. Report for U.S. Environmental Protection Agency.

Simon, F.; Meggyes, T. (2000). Removal of organic and inorganic pollutants from groundwater using permeable reactive barriers. Part 1. Treatment processes for pollutants. Land Contamination and Reclamation, 8: 103-116.

Tratnyek, P. G.; Scherer, M. M.; Johnson, T. J.; Matheson, L. J. (2003). Permeable reactive barriers of iron and other zero-valent metals. In: Chemical Degradation Methods for Wastes and Pollutants: Environmental and Industrial Applications; Tarr, M. A., Ed.; Marcel Dekker: New York: 371-421.

US-EPA (1998). Permeable reactive barrier technologies for contaminant remediation. U.S. Environmental Protection Agency. EPA Report 600-R-98-125.

US-EPA (1999). Field applications of in situ remediation technologies: Permeable reactive barriers. U.S. Environmental Protection Agency. EPA Report 542-R-99-002.