Modelos de otimização para determinação de eficiências de sistemas de tratamento de efluentes sanitários no âmbito de bacias hidrográficas

Abstract

The definition of minimum water treatment efficiencies for wastewater treatment stations located in a watershed represents a complex problem, considering various discharges, presenting different organic loads, disposed to water bodies having different assimilation capacity. This research aims to select optimization models for minimizing water treatment efforts in a watershed. The selected models objective to minimize the sum of efficiencies for the wastewater treatment stations and the inequity between the treatment efforts. Water quality goals were considered as restrictions for the optimization problem that involved dissolved oxygen and biochemical oxygen demand as water quality parameters. Water quality model was integrated with Genetic Algorithm to estimate the set of minimum efficiencies required and to solve the optimization problem. The models were applied at the Pardo river watershed, tributary of Itapemirim river, important river located in Espirito Santo, in Brazil. The results showed that optimization models with equity measures imposed as restrictions to the problem did not guarantee equity, because of the high variation of wastewater loads considered in the watershed. Optimization models that incorporate the equity measure in the objective function showed satisfactory performance, achieving close water treatment efficiencies values.