Permeable reactive barrier (PRB) is a technique for the remediation of contaminated sites.
The operating principle is based on the excavation of a trench downstream of the land to be recovered, which is filled with a reactive material (for instance, capable of degrading pollutants to non-toxic, or less toxic substances); this can be an adsorbent, filtering or biological material capable of degrading contamination. Groundwater movements lead polluted water to transit through the barrier, in which biological and oxidation-reduction reactions take place that lower the concentration of certain pollutants.
The purpose of this technique is to prevent the spread of an existing contamination, released from the soil into the surrounding groundwater, to areas outside the remediation site.
The PRB prototype simulates the spillage of a solution containing petroleum hydrocarbons into a soil area and the slow filtration flow of groundwater through the soil and towards surrounding areas and.
In this way, an artificial contamination plume is produced, which, thanks to the flow of the groundwater, crosses the reactive barrier.
The purpose of the prototype is to analyze the spread of contamination and the barrier’s ability to degrade the contaminant before it crosses it completely.
The prototype consists of a transparent tank, divided into communicating rooms, in which contaminated experimental soil is placed.
A bio-reactive permeable barrier is reproduced in the center of the tank, consisting of a diaphragm filled with a reactive material and capsules inoculated with microorganisms isolated for their ability to deplete the organic contaminants of interest (i.e., TPHs and PAHs).
A combination of modified zeolite and inoculated capsules can be used to obtain a synergetic effect; the zeolites, through their adsorptive function, can lower the hydrocarbon levels by physicochemical adsorption and the capsules, inoculated with competent microorganisms for the contaminants of interest, can remove residual contamination by biodegradation.