Numerical modeling of dissolved oxygen in an ultra-urban best management practice

Stormvault (Jensen Precast, Sparks, Nevada) is a retention-type ultra-urban best management practice, which has been tested extensively for pollutant reduction. As the first step to understand the internal water quality change during a dry-weather condition, dissolved oxygen was monitored in a Stormvault system. A diffusion-reaction model was developed to diagnose the contributions of organic materials floating on the water surface, in the water column, and in the sediment, to dissolved oxygen decrease. The mathematical model was calibrated using the observed dissolved oxygen data recorded at a 0.15-m interval along the water column depth. Three scenarios were simulated, and the results confirmed that sediment oxygen demand (SOD) is the governing factor controlling a dissolved oxygen decrease in the system. The SOD rate reaches 0.8 g m(-2) d(-1) at 20 degrees C, with an average sediment accumulation depth of 0.05 m, which is lower than the recommended cleanup depth of 0.15 m.