Predicting NOM Removal by Fixed-Bed GAC Adsorbers

Natural Organic Matter (NOM) normally exists in raw surface water as a complex mixture of organic compounds, mainly humic acids and fulvic acids. In water treatment plants, free chlorine reacts with NOM and forms a wide range of substances known as Disinfection Byproducts (DBPs). Granular Activated Carbon (GAC) adsorption is one of the best available technologies employed for the removal of NOM. A mathematical model for the adsorption of NOM onto GAC in a fixed bed column and in a batch reactor was built. The mathematical model was solved numerically using finite element and orthogonal collocation methods. Experiments were conducted using Rapid Small Scale Column Test (RSSCT) to evaluate the performance of GAC column to remove or reduce the concentration of NOM in raw water. The predicted values from the mathematical model showed very good agreement with the experimental measurements for a range of empty bed contact time, GAC particle size and raw water pH. Most of the mathematical model parameters were determined experimentally in adsorption equilibrium isotherm and batch reactor experiments.