Modeling of Ocean Outfall Discharges

Bacterial modeling techniques for the San Francisco ocean outfall are reviewed. Extensive oceanographic measurements, and field and laboratory experiments were done. The oceanographic data are briefly reviewed and it is shown that all parameters are subject to considerable spatial and temporal variability. A “wandering puff” model is used to compute the frequency distribution of shoreline bacteria. The model accounts for varying initial dilution due to variation in stratification, current speed and direction, and effluent flowrate, far field diffusion due to oceanic turbulence, spatial and temporal variation in current speed and direction, and diurnal variation in bacterial decay rates. It is predicted that bacterial concentration standards will be met at all shoreline locations without effluent chlorination. Areas of uncertainties in our present knowledge of mixing processes are briefly reviewed, and likely future trends discussed.