Multivariate methods for evaluating the efficiency of electrodialytic removal of heavy metals from polluted harbour sediments

Abstract

Chemometrics was used to develop a multivariate model based on 46 previously reported electrodialytic remediation experiments (EDR) of five different harbour sediments. The model predicted final concentrations of Cd, Cu, Pb and Zn as a function of current density, remediation time, stirring rate, dry/wet sediment, cell set-up as well as sediment properties. Evaluation of the model showed that remediation time and current density had the highest comparative influence on the clean-up levels. Individual models for each heavy metal showed variance in the variable importance, indicating that the targeted heavy metals were bound to different sediment fractions. Based on the results, a PLS model was used to design five new EDR experiments of a sixth sediment to achieve specified clean-up levels of Cu and Pb. The removal efficiencies were up to 82% for Cu and 87% for Pb and the targeted clean-up levels were met in four out of five experiments. The clean-up levels were better than predicted by the model, which could hence be used for predicting an approximate remediation strategy; the modelling power will however improve with more data included.

Comparison of 2-compartment, 3-compartment and stack designs for electrodialytic removal of heavy metals from harbour sediments

“…If sediment characteristics of larger data-sets were included, it is however possible that sediments could be modelled in the same model [23]. When these are not included, optimal remediation conditions for each sediment should be determined on lab-scale prior to proceeding with bench-scale.…”

“…Among the advantages of PLS is that it copes with colinearity between variables and provides plots of the data compressed to fewer dimensions than the original dataset [19][20][21]. In this respect, PLS has proven a reliable tool for assessing the comparative experimental variable importance as well as for predicting experimental conditions for specified remediation objectives for the electrodialytic removal of heavy metals from harbour sediments [22,23].…”

An optimised method for electrodialytic removal of heavy metals from harbour sediments

“…These plots will reflect the relative importance of the model parameters included. The liability of PLS in predicting experimental conditions for specified remediation has also been published elsewhere [24].…”

Contaminated Aquatic Sediments

“…Changes of bacterial abundance and diversity (by a combination of molecular fingerprinting and next generation sequencing analyses) were investigated during biostimulation experiments carried out on anoxic marine sediments characterized by high metal content . Results identified key biogeochemical interactions (Pedersen, Kirkelund et al, 2015). It was noted that remediation time and current density had the highest comparative influence on the cleanup levels that the targeted heavy metals were bound to different sediment fractions.…”