Parametric Analysis and Breakthrough Modeling of Phosphorus from Al-Oxide Filter Media

Adsorptive filtration is becoming a common unit operation/process following a primary unit operation such as volumetric clarification of urban drainage flows and particulate matter. In this study, axial columns packed with aluminum oxide coated media (AOCM) were used to examine breakthrough phenomena and models for total dissolved phosphorus (TDP) at levels typical of urban drainage primary effluent. Mechanistic Langmuir and Freundlich models incorporated a one-dimensional mass balance, transport equation, mass transfer model, and initial and boundary conditions. Parameters of the mechanistic models were determined by isotherm and kinetics testing of TDP adsorption on AOCM. Empirical Thomas model and empirical bed-depth-service-time model were also examined. Measured TDP adsorption breakthrough curves (BTCs) demonstrated typical “S-shaped” curves. Results indicated that smaller AOCM media (higher specific surface area), slightly acidic pH, lower TDP concentrations, and lower surface loading rates generated increased breakthrough capacity. While ${\text{Ca}}^{2+}$ enhanced, and ${\text{SO}}_4^{2-}$ inhibited breakthrough capacity, combined at urban drainage concentrations, these interactions were small compared to other tested parameters. Media capacities determined by BTC were smaller than isotherm capacities of longer contact time. Results indicate that the Thomas model most consistently reproduced measured BTCs within the range of typical urban drainage conditions.