Development of a low-temperature thermal treatment process for the production of plant-growable media using petroleum-impacted dredged sediment

Abstract

In this study, we investigate the potential of low-temperature thermal treatment to treat petroleum-impacted sediments to produce plant-growable media. The thermal treatment posed a marginal or moderate effect (i.e., 6–47% change) on most of the sediment physicochemical properties, including organic carbon, nutrient contents, and cation exchange capacity, while exhibiting a total petroleum hydrocarbon removal efficiency of 93%. The treatment reduced the bioavailability of heavy metals in the sediment, which was attributed to enhanced physical and/or chemical barriers against heavy metal leaching by sediment particle aggregation and carbonaceous matter formation. Because the oxidation of sediment constituents generated new plant stressors, water-soluble organics and sulfate salts, the thermal treatment by itself was insufficient to produce a medium favorable for the germination and growth of barley. These newly generated stressors were easily removed by water washing post-treatment to yield a final product that showed excellent performance in supporting barley germination and growth. This study demonstrates the benefit of low-temperature thermal treatment to simultaneously achieve control over source-originated contaminants and preserve the ecological value of the dredged sediments. This study also identifies plant stressors that were generated during the treatment, and describes an effective control strategy against them.