Desorption of compounds during operation of GAC adsorption systems

Abstract

Desorption of previously adsorbed compounds from granular activated carbon beds is a problem that can produce effluent concentrations that are temporarily greater than influent concentrations. The research reported in this article was performed with a verified mathematical model to evaluate factors affecting desorption caused either by a reduction in influent concentration or by competition. The factors studied were mass transfer coefficients, equilibrium capacity characteristics, and process variables (bed length, hydraulic loading, and carbon particle size). For conditions roughly approximating treatment plant operation, results indicate that the time during which the concentration in the effluent is higher than that in the influent can be significant, possibly on the order of weeks. A system designed for efficient adsorption may also provide for efficient desorption.