Name: Franciane Entringer Curbani
Type: MSc dissertation
Publication date: 12/07/2016

Namesort descending Role
Julio Tomás Aquije Chacaltana Advisor *

Examining board:

Namesort descending Role
Gilberto Fonseca Barroso External Examiner *
José Antônio Tosta dos Reis Internal Examiner *
Julio Tomás Aquije Chacaltana Advisor *

Summary: Water quality is the result of natural conditions and the land use in the drainage basin. The depletion of dissolved oxygen (DO) due to excessive input of nutrients from domestic or industrial effluents is one of the most important issues in estuarine water quality. Water quality studies that require an understanding of the processes that occur in the water body requires a comprehensive spatio-temporal analysis to identify cause and effect relationship, therefore numerical models are important tools for such analyzes. In this work a numerical model, based on computational fluid mechanics and transport phenomena, was applied to understand physical and biochemical process governing the water quality of the Vitória Island Estuarine System (ES, Brazil). The following constituents were analyzed: NH4+, NH3, NO3-, BOD5 and DO. These constituents participate in the DO balance. In addition, nitrification, mineralization and reaeration processes were also analyzed. Based on these constituents and processes the following aspects were evaluated: the addition or removal of the constituents by each process; the effect of punctual urban sources in the DO balance and the spatial distribution of the constituents concentrations in moments of maximum and minimum dilution, correlating them to the hydrodynamic fields. The reaeration was an important process for introducing DO in Vitória Bay, responsible for up to 53% of DO in the middle estuary. The primary loss process of DO was the mineralization, followed by the nitrification. The reduction of DO concentration due to punctual urban sources was minimal (local maximum of -2.1%). The DO concentration at the spring tide was higher than at the neap tide, which was associated with higher dilution of the constituents in the bay during spring tides, due to the larger volume of water and the higher currents velocities. The critical instants for the concentration of the constituents occurred in ebb low water during neap tides, with lower dilution related to weak currents and lower volume of water from the Espírito Santo Bay. At the region of the Itanguá River and Costa Channel it was observed increased deterioration of water quality, and the middle estuary was the most affected area by the considered inputs of nutrient and BOD.

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