Controlling Soil and Water Acidity in Acid Sulfate Soil Terrains Using Permeable Reactive Barriers

Abstract

There are about 12–14 million ha of acid sulfate soils (ASSs) found throughout the length and breadth of the earth. Bridge and building foundations, pipelines, culverts, and other buried infrastructure in such acidic environments are deteriorated when they are exposed to higher acidity, which is generated due to leaching of sulfuric acid from ASS. Thus, acidic groundwater should be properly treated to avoid detrimental effects on natural environment and strenuous efforts on repairing damaged manmade structures. Since the early 90s, permeable reactive barriers (PRBs) were implemented in several places worldwide and it was proven that PRBs are capable of competently treating poor-quality groundwater with various contaminants. While the acidic groundwater flows through a PRB, contaminants (toxic cations) are removed by mineral precipitation and due to the chemical reactions occur, a near-neutral pH is maintained in the effluent. Nevertheless, longevity of the PRB is alleviated due to coupled clogging in porous media. Physical, chemical, and biological clogging mechanisms and the existing PRB design criteria have been critically reviewed in this paper, including precursory numerical models. It is imperative to extend existing equations and models combining all possible clogging mechanisms, to assure the maximum acid removal capacity of a PRB. Hence, water and soil quality would be enhanced to make the land safe for transport and other infrastructure developments.