Selection of permeable reactive barrier materials for treating acidic groundwater in acid sulphate soil terrains based on laboratory column tests

The Shoalhaven region of NSW experiences environmental acidification due to acid sulphate soils (ASS). In order to trial an environmental engineering solution to groundwater remediation involving a permeable reactive barrier (PRB), comprehensive site characterisation and laboratory-based batch and column tests of reactive materials were conducted. The PRB is designed to perform in situ remediation of the acidic groundwater (pH 3) that is generated in ASS. Twenty-five alkaline reactive materials have been tested for suitability for the barrier, with an emphasis on waste materials, including waste concrete, limestone, calcite-bearing zeolitic breccia, blast furnace slag and oyster shells. Following three phases of batch tests, two waste materials (waste concrete and oyster shells) were chosen for column tests that simulate flow conditions through the barrier and using acidic water from the field site (pH 3). Both waste materials successfully treated with the acidic water, for example, after 300 pore volumes, the oyster shells still neutralised the water (pH 7).