Field and Numerical Investigation of Mixing and Transport of Ammonia in the Ottawa River

• Main Author: Vouk, Ivana
• Other Authors: Mohammadian, Abdolmajid
• Language: en
• Published: Université d'Ottawa / University of Ottawa 2016
• Subjects: effluent; river mixing; ammonia; multiport diffuser; CFD modelling; Ottawa River
• Online Access: http://hdl.handle.net/10393/34098; http://dx.doi.org/10.20381/ruor-5947

Wastewater treatment plants discharge effluents containing a number of constituents whose concentrations may negatively affect the receiving waters. Current research in mixing and transport between a point source discharge and the ambient environment attempts to reduce these effects through a better understanding of the physical processes involved and development of numerical models to better predict the fate of the effluents under different conditions. This thesis examined the mixing and transport of ammonia discharged from a multiport diffuser of a municipal wastewater treatment plant into the Ottawa River. The river reach was surveyed using an M9 acoustic Doppler current profiler to obtain spatially distributed measurements of depth and velocity. Water samples were collected at and downstream of the diffuser at multiple depths. The samples were analyzed for ammonia concentration and kinetics. The river reach was also simulated in the FLOW-3D model using available turbulence closure schemes. Comparisons were made between measured and modelled results, as well as some empirical and semi-empirical approximations. A combination of measured and modelled results helped describe (quantitatively and qualitatively) the mixing and transport between the discharged effluent and receiving river. Unionized ammonia was tested for regulatory compliance. Both measured and modelled results showed that although the regulatory end-of-pipe discharge concentrations were met, downstream regulations were not met.