Physical and CFD Modeling of Runoff Particulate Matter by Partial Exfiltration

In many green infrastructure systems and low impact development systems, mechanistic control has occasionally been investigated. Also only selected studies have modeled the performance of such systems under transient and unsteady conditions. Therefore in this study, the computational fluid dynamics (CFD) model was applied to simulate the performance of an existing green infrastructure system, a stormwater partial exfiltration system (PES), located on Interstate Highway 75 (I-75) in Cincinnati, Ohio. The system comprises a linear porous media reactor of oxide-coated granular substrate media (OCS) capped by an infiltrating surface of cementitious permeable pavement (CPP). Results indicate that the CFD model is a feasible and accurate tool to simulate the performance of PES in three circumstances: stochastic storm events (unsteady flow), different influent flow rates (steady flow), and long-term performance (on an annual basis). For unsteady flow simulation differences between modeled and measured effluent PSDs are not significant for the database of monitored events. For event simulations, removal efficiency of particulate matter (PM) is greater than 90% for the PES under any flow rate conditions. Considering annual infiltrated flows only, the PM removal efficiency of the PES is 97%. If annual infiltrated and bypass flows over the CPP (combined, the influent to the PES) are considered, the PM removal efficiency is 68% based on continuous simulation for a year of data.