Gustavo Passos, Tobias Bleninger
Wednesday 1 july 2015
9:00 - 9:15h at Antarctica (level 0)
Themes: (T) Special session, (ST) Marine outfall system
Parallel session: 8D: Special Session: Marine Outfall System
A significant portion of the world´s population lives in coastal cities and their main economic activities occur along the coast and are heavily dependent on good water quality. Deciding which is the best alternative in the treatment of the wastewater is a complex technical and financial decision in order to achieve the quality standards required by legislation. Aiming to assist designers and environmental control offices, this work will demonstrate the effects that different effluents and discharge configurations have on marine waters. The method uses CORMIX, a hydrodynamic modeling software which is based on an integral method, capable of predicting the geometric characteristics and dilution of the initial mixing zone. The model was run in a time-series mode, representing one data month with the change in the environment and effluent characteristics which occur each time step, with the field data obtained for the project of the submarine outfalls of Cartagena, located in Colombia. This series was simulated by CorTime, a post-processing submodule of CORMIX, for nine study scenarios. There were three effluent types (sewage, cooling water and industrial effluents) discharged by three different discharge configurations (multiport diffusers, submerged single tube and channel with free surface). The results obtained with the time series were representative to the field data used and help analyzing the plume behavior and variability of each scenario. The best dilution occurred to the multiport diffusers (198 _ S _ 1839) with well distribuited plumes until the depth, by the major contact between the effluent and the marine waters. The other discharges presented dilutions under 100, with lower efficiency, thin plumes (less than 2,4 m), concentrated on the surface (sewage) or on the sea bottom (industrial effluent). These cases need greater investment in effluent treatment, they cause greater environmental impact, visual aspect concerns on the surface and the ecosystem on the sea bottom. The plume of the onshore channel discharge configuration always reached the coast, thus having the potential of problems related to bathing water quality.