FIELD-TESTS ON SMALL MARINE OUTFALL

Field tests were performed on a small marine outfall discharging mesti c wastes. Dye was injected into the effluent flow entering the pump ho use and samples were taken in the sump and offshore in the sewage boil . Dilutions were evaluated from the sample concentrations and compared with theoretical predictions. Data were first collected with the outf all discharging freely in the horizontal direction. Following these te sts a mixing tube was attached to the outfall. This consisted of a hor izontal cylinder designed to provide some predilution before the efflu ent jet entered the receiving water. Data were again collected after t he mixing tube was installed and the dilutions measured were compared with theoretical predictions. These showed that the theory used for th e mixing tube under-predicted measured values by more than 25%.