Activated carbon load equalization of transient concentration spikes of gas-phase toluene

Biofilters used for air pollution control often experience diminished treatment performance when subjected to transient periods of elevated contaminant concentrations. In research reported here, the potential for using granular activated carbon (GAC) columns to attenuate peak loading of highly variable toluene concentrations was investigated through a combination of experimental testing and numerical modeling. The experimental regime included testing of GAC columns subjected to isolated spikes in toluene concentration as well as complex loading patterns involving multiple spikes in series, intended to simulate the highly dynamic, complex loading conditions commonly encountered in industrial applications. A MATLAB code was used to implement a pore and surface diffusion model to allow simulation of transient loadings of varying intensity and short duration. Collectively, experimental and modeling results demonstrate that passively operated GAC columns with short contact times can accumulate toluene present in waste gases when influent concentrations are temporarily high and later desorb and redistribute the toluene at comparatively lower concentrations over a longer time period when influent concentrations are lower. Such processes have the potential to dampen shock loading to a downstream biofilter or other air pollution control device, and thereby improve treatment performance.