Optimisation of the operation of an electrochemical process to treat TBT-contaminated sediments on a pilot scale

Since at least three decades tributyltin had been commonly used in paint formulations to protect ship hulls and submersed surfaces from fouling. This has resulted in negative effects to the marine environment due to its high toxicity towards non-target organisms and to its accumulation in sediments, especially near point sources of pollution. Even if a ban of TBT for its application in anti-fouling paints is enforced the problem of TBT-contaminated sediments will remain for the coming years due to the low degradation rates of organotin in sediments. In this work an electrochemical process at a pilot scale to destroy TBT in sediments was investigated. Previous experiences at a laboratory and technical scale have demonstrated the potential of this process to electrolytically degrade organotin species in sediments. This article deals with the optimisation of the pilot plant performance in terms of organotin degradation and operation costs monitoring additionally the effect of the electrochemical treatment on other pollutants such as heavy metals, PCBs, and PAHs. The aim was to investigate by means of a parametric study the range of operating conditions required to destroy TBT down to concentrations lower than 100 mug/kg; to determine the influence of those parameters on the performance of the process; and to evaluate the operation costs associated to the process. It was determined that it was possible to destroy 2 and chloride TBT down to 100 mug/kg at current densities in the range of 4.4 to 6.6 mA/cm(2) concentrations of least of 0.2 mol/L with operation costs of 13 to 18 EUR/m(3).