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.摘要 本研究旨在提出一种方法，以支撑基于流量历时曲线（Flow-Duration Curves）与自净分析等水质参数，划定符合巴西国家环境委员会（CONAMA）第357/2005号决议的河流水质等级。为构建不同模拟水质情景，本研究纳入三类与不同生化需氧量（BOD）去除效率相关的污水处理工况、两类有机负荷工况，以及三个时间基准（2014年、2020年与2030年）。针对位于巴西圣埃斯皮里图州南部的帕尔杜河，本研究应用QUAL-UFMG模型开展自净能力评估，模拟过程仅考虑流域内污水排放，选取BOD与溶解氧（DO）作为核心参数。研究绘制了与CONAMA第357/2005号决议中1、2、3类河流环境标准对应的BOD流量历时曲线（BOD Flow-Duration Curves）。结果表明，借助河流自净建模评估地表水水质以划定河流水质等级具备重要应用价值；同时，针对水质流量历时曲线采用非确定性方法，可有效简化渐进式水质目标制定的决策流程。