Combined use of river water quality flow-duration curves and modeling as a tool to support class definition according to conama 357/2005 regulation

ABSTRACT

This study aimed to propose a methodology to support the establishment of Brazilian CONAMA 357/2005 rivers water quality classes based on quality parameters Flow-Duration Curves and self-purification analysis. To establish the different simulation water quality scenarios three sewage treatment conditions associated with distinct biochemical oxygen demand (BOD) removal efficiencies, two organic loads conditions and three time horizons (2014, 2020 and 2030) were considered. The QUAL-UFMG model for assessment of the self-purification capacity of the Pardo river, located in the south of Espírito Santo state, Brazil, was applied considering the BOD and dissolved oxygen (DO) parameters. In the simulations only river watershed sewage discharges were considered. BOD Flow-Duration Curves associated with environmental standards established by CONAMA Resolution 357/2005 for classes 1, 2 and 3 rivers were drawn. The results indicate the great importance of using river self-purification modeling for assessment of surface water body quality to establish river water classes. The results also indicate that a non-deterministic approach to water quality Flow-Duration Curves facilitates the decision-making process for the establishment of progressive water quality objectives.

Keywords:
Classification of surface water rivers self-purification capacity; Quality Flow-Duration Curves; Domestic sewage