Modeling and plume tracking study of a Newfoundland coastal outfall.

摘要

Marine pollution is a serious environmental problem facing many industrialized and developing countries. It has short-term and long-term impacts on the ecological systems, human health, and economy. These impacts can be minimized through proper offshore and coastal zone management, continuous monitoring, and enforcement of regulations. Outfall disposal can be an effective environmental and economical method for discharging treated industrial and municipal effluents to the marine environment. This is because the dynamic nature of the ocean can enhance the dilution process of the effluent. However, if the outfall is not properly designed and monitored, it may have negative impacts on the marine biota and public health. Well designed outfalls result to better effluent mixing within the ambient water.;In this work, the performance of an existing staged diffuser outfall design, at Spaniard's Bay, was evaluated using the Cornell Mixing Zone Expert Model (CORMIX) length scale model and compared with an alternative T-Shape riser design using Roberts, Snyder and Baumgartner (RSB) length scale model. The existing staged outfall design provided a better near-field dilution than the T-Shape riser for shallow coastal waters. For model validation and water quality assessment, an environmental monitoring experiment was carried out around the Spaniard's Bay outfall. An Autonomous Underwater Vehicle (AUV) and towed sensor platforms were used for monitoring salinity, temperature, turbidity, chlorophyll a, and dissolved oxygen. The data were statistically analyzed and mapped for plume tracking and water column assessment purposes. Turbidity and salinity observations were investigated as a natural tracer of the effluent. The turbidity values were decreasing while moving from the effluent boil to a downstream direction. The salinity variations were also decreasing while moving from the outfall to a downstream direction. The low salinity and high turbidity results of more than 13000 in-situ observations were positively correlated. As for the water quality status, the dissolved oxygen percent saturation and chlorophyll a concentrations were not significant indicating a good water circulation in the bay. The experiment results demonstrated that effluent plume can be traced by in-situ monitoring of turbidity and salinity as natural tracers. These parameters were also applied for near-filed hydrodynamic model validation.