Tracer techniques to evaluate the dilution performance of sewage submarine outfalls

Fluorescent dye tracers were used to label industrial and domestic sewage discharged in the sea water by multiport submarine outfalls in order to evaluate the effluent dilution pattern. Uranine and Amidorhodamine G were simultaneously injected in the outfall's pipeline during 6 to 8 hours by a continuous injecting device and detected at different depths in the receiving coastal water. In order to obtain sufficiently detailed information to plot the sewage dilution plume, a large number of samples with known coordinates must be taken in the field. Computer programs to assist the navigation of the monitoring boat and to analyze the obtained data in the laboratory are essential. This paper shows how fluorescent dyes can be used for evaluating the dilution pattern of effluent in the sea water and to provide valuable answers for hydrodynamic and water quality modeling.