Development of a performance threshold approach for identifying the management options for stabilisation/solidification of lead polluted soils

Two soils spiked with lead at different rates were stabilised/solidified using Portland cement and fly ash at different soil:binder ratios, and tested for their setting time, unconfined compressive strength, leachability and durability. A performance threshold approach was used in order to identify optimal management options for the products of the S/S treatment. Results show that soil texture, percentage of binders and lead concentration play an important part in the treatment, significantly influencing the performance of the resulting products in terms of curing, compressive strength and durability. Pb soil concentrations higher than 15000 mg kg-1 were found to heavily reduce the applicability of the treatment requiring the maximum amount of binder in order to satisfy the performance criteria. The performance of sandy soils was shown to be limited by setting time and UCS features due to the retardation of the hydration reactions and also by its leaching behaviour, whereas for silt-clayey soils the critical parameter is the mechanical resistance. © 2014 Vilnius Gediminas Technical University (VGTU) Press

Environmental Life Cycle Assessment of marine sediment decontamination by citric acid enhanced-microwave heating

The potential ability of microwave heating (MWH) for the remediation of marine sediments affected by severe hydrocarbon (HC) contamination was investigated. Decontamination effectiveness and environmental sustainability through a comparative Life Cycle Assessment (LCA) were addressed. Main results revealed that the application of a 650-W MWH treatment resulted in a rapid (15 min) HC removal. A citric acid (CA) dose of 0.1 M led to enhanced-HC removals of 76.9, 96.5 and 99.7% after 5, 10 and 15 min of MW irradiation, respectively. The increase in CA dose to 0.2 M resulted in a shorter successful remediation time of 10 min. The exponential kinetic model adopted showed a good correlation with the experimental data with R2 values in the 0.913–0.987 range. The nature of the MW treatment was shown to differently influence the HC fraction concentration after the irradiation process. Achieved HC removals in such a short remediation time are hardly possible by other clean-up techniques, making the studied treatment a potential excellent choice. Removal mechanisms, which allowed the enhanced-MWH to operate as a highly effective multi-step technique (pure thermal desorption + chemical washing), undoubtedly represent a key factor in the whole remediation process. The LCA highlighted that the MW technology is the most environmentally sustainable alternative for sediment decontamination applications, with a total damage, which was 75.74% lower than that associated with the EK (0.0503 pt)