Planejamento de sistemas de tratamento de efluentes no âmbito de bacias hidrográficas com base em modelagem de qualidade da água e técnicas de otimização

Abstract

In Brazil, the sewage treatment services coverage levels are low. Sewage treatment systems setting up, operating and maintaining costs are generally high and vary considerably depending on the technology type to be implemented. Given this scenario, this research proposed a method for planning effluent treatment systems involving minimization of sewage treatment and transport costs, considering the current legislation, systemic vision in which the river basin is assumed as a planning unit and water bodies self-depuration capacities. The integrated modeling was supported by three modules: (i) water quality mathematical modelling combined with optimization technique to estimate minimum sewage treatment efficiencies, (ii) hydraulic calculations and (iii) Facility Location Problem (PLF). The study differs from others by integrating organic material removal efficiencies into Wastewater Treatment Plant (WTP) locations choice process, by considering self-purification capacity of water bodies and by discussing Consortium Effluent Treatment (CET). In the CET, the effluents generated by different point sources are transported and grouped in ETEs presenting greater capacities, providing centralized networks. The methodology was applied to the Pardo watershed, in Espírito Santo state, Brazil. In total, 22 scenarios for water quality modeling were created, subdivided into two groups: individual WTPs and CET. In order to consider the method's sensitivity to parameter variations, four analysis quadrants were developed being a key concept worked in each of them. The adoption of the CET concept proved to be viable, especially for networks presenting smaller lengths, sets of high sewage treatment efficiencies and/or increased scale economies. When considering the growing global population and cities facing budget constraints, paradigms changes and search for economically and environmentally safe solutions are very valuable.