Diffusion of Sewage Effluent from Ocean Outfall

Full scale diffusion experiments were conducted during August and December 1968 to estimate coliform bacteria concentration patterns of sewage effluent from an ocean outfall located at Pompano Beach, Florida. The experiments included measurements of near-shore currents, estimates of turbulent diffusion of the sewage effluent and the determination of natural die-off of coliform bacteria. It was found that the near-shore currents are predominantly towards the North with fluctuations in speeds produced by the meandering of the Florida Current, by wind and tidal effects, and by inlet waters. The diffusion data indicate that for the travel times of interest, concentrations can be reduced by a factor of 1000 or more. Coliform bacteria die-off rates were found to be approximately two orders of magnitude greater during the summer months than during the winter. A model was developed to predict downstream concentration patterns and the results can be used to assess future ocean outfall installations.