Abstract

This study describes the development of a particle-tracking model which predicts the trajectories of particles that apportion wastewater effluents discharged into coastal waters. The subsequent spreading of the effluents is simulated by a large number of particles evolving as clouds. The evolving cloud patterns are predicted for given time-dependent ambient currents and density stratification. The model allows for advection, non-Fickian horizontal diffusion and Richardson number-dependent vertical diffusion. The model is applied to a discharge of wastewater effluents into Burrard Inlet in British Columbia, Canada, where the ambient currents are tidally-driven and the ambient stratification results from river freshwater inflows. This application uses field measurements of ambient conditions as model input. Vertical profiles of effluent concentration derived from simulated particle distributions compare well with field measurements of effluent concentration. The model has shown advantages in handling large spatial gradients of the concentration field, and serves as a useful water-quality modelling tool.