Ex Situ Sediment Remediation Using the Electrokinetic (EK) Two-Anode Technique (TAT) Supported by Mathematical Modeling

Heavy metals are non-biodegradable environmental pollutants, and if present in sludge/sediment in elevated concentrations, they can cause serious problems. In this paper, the possibility of applying two-anode electrokinetic treatment was investigated for the ex situ remediation of copper (Cu) and nickel (Ni)-contaminated sediments. The influence of the following parameters on the treatment efficiency was investigated: applied electric field, physicochemical changes in the system, and the characteristics of the pollution (concentration and forms of metal occurrence). Additionally, based on the results of the sequential extraction procedure, a risk assessment of sediment before and after treatment was performed. Also, we developed a mathematical model that allows us to define the time required to reduce nickel and copper to non-hazardous levels from contaminated sediment via electrokinetic treatment. The results obtained indicate that changes in the pseudo-total content and changes in Cu and Ni availability along the electrokinetic cell are consistent with the physicochemical changes in the sediment. The amount of applied electric field does not notably affect the treatment efficiency in most cases. Based on the results, the majority of samples of treated sediment can be dislocated without special protection measures. The most acceptable treatment for ex situ remediation is the one with solar panels, as it is considered economically and environmentally most appropriate. For this treatment, according to risk assessment code, the risk was found to be low (Cu) to moderately low (Ni). Since more than 50% of Cu and Ni content is related to the organic and residual fraction, and based on the physicochemical conditions and high percentage of clay, we can assume that there are no environmental hazards. This work serves as a starting point for the developed mathematical model that has proven to be very promising for prediction of the time necessary for sediment metal remediation.