Investigation of climate change effect mitigation of thermal wastewater jets discharged into the sea by Visual Plumes model

Thermal power plants on the coast often use large amounts of seawater in cooling processes with open-cycle cooling systems. This cooling water is discharged from the plant back into the receiving ambient as a high-temperature wastewater. The discharged thermal wastewater moves towards the water surface due to its density. Thermal wastewater discharge can negatively affect the aquatic ecosystem. In addition, by increasing the surface water temperature, it can reduce the carbon dioxide absorption capacity of the receiving ambient and increase evaporation on the water surface. The increase in the amount of water vapor and carbon dioxide, which are greenhouse gases, in the atmosphere can contribute to the increase of the greenhouse effect. Thus, thermal wastewater discharge can be an important factor that can increase the negative effects of climate change by warming the atmosphere more. Therefore, increasing thermal wastewater dilution capacities by using advanced design methods in new marine outfall systems or improving the existing thermal wastewater outfall systems can help mitigate climate change. In this thesis, it is aimed to reduce the contribution of thermal wastewater discharges from thermal marine outfalls carried out with horizontal nozzles to climate change by increasing the impact point dilution. Within the scope of the thesis, various scenarios were created according to different receiving ambient conditions of thermal wastewater discharged with +10°C temperature from the conventional horizontal discharge port into the stagnant and unstratified density having receiving ambient. According to the discharge scenarios, wastewater jet geometry and impact point dilution were investigated using US EPA, VP-UM3 numerical model. Then, improvement options were investigated according to the current status of the dilution performance by changing the vertical inclination angle, diameter and depth of the discharge port. The examined discharge nozzle diameters were 0.1m; 0.2m and 0.5m, ambient density 1015-1035 kg/m3 (typical value 1025 kg/m3), densimetric Froude number 20, discharge port depth 10m-50m, discharge port vertical inclination angle (-80°)-(+80°), ambient temperature 15°C-25°C were selected. As a result of the study, it was determined that the downward inclination of the nozzle showed increments of the impact point dilutions maximum 6.27% compared to the horizontal discharge. In the case of downward inclination discharge of the port area reduced by half, it was determined that the impact point dilution increased maximum 95.15% compared to horizontal discharge. These increases in the impact point dilutions of thermal wastewater marine outfall discharges could be helpful to reduce the contribution of these facilities to global warming.