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Preliminary Design of a River Wastewater Outfall and Associated Treatment System

Author(s): D. N. Bottelli; G. Nociari; S. H. Martijena

Linked Author(s): Diego Norberto Bottelli

Keywords: Wastewater river outfall; Fickian model for sensitivity analysis; 2D hydrodynamic modeling; CFD; Preliminary treatment; UV disinfection for pretreated wastewater

Abstract: This paper presents the studies carried out for the preliminary design of an outfall for disposing wastewater (0.86 m3/s) from Zárate city (Argentina) into the Paraná de las Palmas River (mean flow of 4,600 m3/s) and the determination of the level of treatment required. Bacterial concentration was taken as the main water quality parameter for design. This work includes two main subjects: a dispersion analysis that includes the application of an advection-diffusion model (Fickian model) under uniform flow for transverse mixing in order to perform sensitivity analysis of different design variables, 3D CFD modeling to study mixing in near field, and 2D hydrodynamic and Lagrangian water quality modeling for far field analysis. The comparison between the results obtained from the different dispersion models is presented and it demonstrates the validity of the simplest models for preliminary design. The second subject is the study of the level of treatment required, which includes an analysis of disinfection of pretreated raw wastewater with Ultraviolet (UV) radiation, defining the treatability boundaries for this process regarding raw wastewater characteristics in terms of Suspended Solids and Turbidity, also considering UV absorbance. The results of the analysis obtained so far show the feasibility of combining preliminary treatment, UV disinfection and a single discharge outfall to reach required water quality parameters in the river. The next stages of the project include more studies about UV disinfection by additional laboratory analysis, new tests on the pilot UV plant and CFD modeling of the UV reactor. . Since there are many cities in South America, and particularly in Argentina, that discharge raw wastewater directly on the coastline of rivers with similar characteristics to the one studied on this paper (high flows with considerable capacity of dilution), it is expected that the methodology presented here can contribute to simplifying the design process for outfall systems, reducing the cost in wastewater treatments and increasing the selection of outfall systems as one of the main strategies for decreasing the pollution of large water streams in our region and similar areas around the world.


Year: 2016

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