Prospects for reducing the contribution of organic load in a water basin with significant urban occupation

Abstract

The prospects for reducing organic load in water basins must be evaluated considering the self-purification capacities of the water bodies into which the raw or treated effluent will be discharged. The aim of this work was to evaluate the reduction of the organic load contribution to the Poti River, a watercourse that crosses the city of Teresina, Piauí, Brazil, considering different conditions for the final disposal of domestic sewage. To estimate the levels of reduction of the organic load contribution, the Water Quality Model Qual-UFMG and Nonlinear Programming were used in a combined manner. Three scenarios of final effluent disposal were modeled. For the appropriation of the reductions in organic load contributions, two different optimization models were used, models that incorporated restrictions based on the environmental quality standards indicated by the Brazilian Environment Council (CONAMA) Resolutions No. 357/2005 and 430/2011. The results indicated that the estimated effort for removal of organic load based on the optimization model that does not employ an equity measure among discharges was lower, regardless of the scenario analyzed. Additionally, in the simulation scenarios in which the quality standards for effluent were not considered, the efforts for removing organic load were lower, regardless of the optimization model used.