Type: MSc dissertation
Publication date: 01/10/2018

Namesort descending Role
José Antônio Tosta dos Reis Advisor *

Examining board:

Namesort descending Role
José Antônio Tosta dos Reis Advisor *

Summary: The proper assessment of effluent treatment systems implies multiple objectives, being has the most relevant the removal of pollutants which might harm the receiving water body. The level of treatment required depends on effluent characteristics, receiving water course class uses from the and self-purification capacity. In the sewage treatment system selection process attention is mostly directed towards the control of the organic matter input, since it is the main responsible for dissolved oxygen consumption. Nevertheless, it must be emphasized that other components must also be evaluated in the selection process. Nitrogen is a parameter of great importance for the control of water pollution, since, among the nitrogenous matter convertion processes, nitrification implies in water oxygen consumption, in addition to the toxic behavior of some forms of nitrogen. The present study employed, for the watershed area of River Pardo (Espírito Santo, Brazil), mathematical water quality modeling combined with the optimization technique to estimate the minimum organic matter and nitrogen removal efficiency and to pre-select sewage treatment systems. Quality standards associated with the BOD, DO and nitrogen parameters for fresh water bodies’ uses classes constituted the constraints to the problem. The computing program developed in the MatLab software environment and based on the mathematical formulations of the QUAL-UFMG model, associated with the Genetic Algorithm, allowed the appropriation of BOD and ammonia efficiencies for the river basin effluent treatment systems for the scenarios considered. Sewage treatment systems were pre-selected, according to the estimated efficiencies observed for districts Ibatiba, Irupi, Iúna, Santíssima Trindade and Nossa Senhora das Graças districts. Considering the quality standards established for class 2 rivers, it was observed that the amount of pre-selected treatment alternatives for waters presenting pH between 7.5 and 8.0 were lower than those that associated with waters presenting pH lower or equal to 7.5 since, with the increase in the pH for water courses, the systems need to be more efficient in the ammonia removal, due to the potential increase of its toxicity.

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