Evaluation of Offshore Wastewater Outfall and Diffuser

Copyright © 2013 Emmet M. Owens et al. This is an open access article distributed under the Creative Commons Attribution Li-cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Outfall alternatives are evaluated for a municipal wastewater treatment facility that discharges effluent at the shoreline of an urban lake. Occurrence of plumes of poorly diluted effluent in adjoining portions of the lake is described. Alterna-tives considered include outfalls over a range of depth and various diffuser designs. Benefits and impacts on lake strati-fication and dissolved oxygen are evaluated for an array of design alternatives with a model which links a far field hydrothermal and transport submodel with a near field buoyant plume submodel. Outfall design features are described that: 1) reduce shoreline discharge of bypass flow of partially treated wastewater during major runoff events; 2) elimi-nate plumes of poorly diluted effluent; and 3) reduce loading of the effluent to the upper waters. A deep (10 to 14 m) outfall with a multiport diffuser would reduce the loading of the facility’s effluent to the upper waters by approximately 40%, without noteworthy impact on stratification or dissolved oxygen