Prediction of fixed-bed GAC filter consumption for complex VOC mixtures using a parsimonious competitive adsorption model and a single batch test

The design of fixed-bed adsorbers for the treatment of drinking water and wastewater contaminated with complex mixtures of organics is a tedious procedure that requires detailed description - using a combination of experiments and modelling - of the individual and competitive adsorption behaviour of many dissolved species. To address the need for an experimental and modelling workflow that is both accurate and parsimonious, this study systematically evaluates the treatment of groundwater contaminated with 13 competing chlorinated hydrocarbons using a fixed-bed of granular activated carbon (GAC). Firstly, a single batch test, interpreted using a competitive Freundlich adsorption model, was demonstrated to be an effective alternative to multiple single-component tests for determining single-compound isotherm parameters. The isotherm parameters of the 13 chlorinated hydrocarbons were estimated from the batch test using both the Ideal Adsorbed Solution Theory (IAST) and the simplified IAST (SIAST) models, with the latter model emerging as more parsimonious and robust based on Akaike’s information criterion. Then the experimental breakthrough and solid phase concentrations of the 13 compounds in a fixed-bed system were accurately predicted by implementing an equilibrium competitive adsorption transport model. The good agreement between the fixed-bed adsorption data and the competitive model confirmed and validated the whole approach. Compared to standard approaches based on mass balance considerations or rapid small-scale column tests, the proposed procedure enables quicker and easier scaling up of a multispecies sorption behaviour from a single batch test, thus reducing the experimental and modelling effort needed for the dimensioning of full-scale adsorbers for treating many-component mixtures of contaminants in aqueous matrices.