AbstractIn the urban water cycle, adsorption facilitated by engineered granular media increasingly is deployed for solute separation in potable water, stormwater, and wastewater systems. Of these systems, stormwater treatment is inordinately complex. Stormwater systems are passive, decentralized, and subject to highly unsteady and uncontrolled fluxes with multiphase interactions. This study proposes a multiphase and multiphysics computational fluid dynamics (CFD) model, interAdsFoam, to simulate turbulence mixing and adsorption with dynamic water–air interface and reaction zones. An original CFD model is proposed, benchmarked, and validated with data sets across a range of scales: (1) bench-scale columns for model parameter estimation, (2) physical modeling of a radial flow adsorption reactor (RFR) subject to controlled fluxes, and (3) field monitoring of a commercial volumetric radial flow adsorption reactor (VRFR) system subject to uncontrolled event-based fluxes. The results illustrate (1) the nonuniqueness of numerical solutions for parameter estimation in adsorption modeling; (2) that regulating the parameter estimation process with isotherms improves model generalizability; (3) inverse modeling of the RFR hydraulic resistance with the quadratic Thiem model can provide a more accurate representation than the Ergun model; and (4) that turbulence transport and chemical adsorption are dynamically coupled with the air–water momentum balance. The proposed CFD model predicts total dissolved phosphorus (TDP) transport and fate based on field monitoring of the VRFR. System dynamics and treatment functionality are elucidated, and implications for practical reactor design are discussed. The proposed open-source CFD model provides a novel framework for higher-fidelity urban water adsorption reactor simulation, design, and optimization than current methods for adsorption.