Table 02 - Evaluation of parameters according to the classification of CONAMA Resolution No. 357/05

The analysis of the physicochemical and microbiological parameters of the stream reveals significant water quality degradation, consistently exceeding the limits set for Classes 2, 3, and 4 (likely based on Brazilian environmental standards). The Dissolved Oxygen (DO) had an average concentration of $4.7\ \text{mg/L}$, which is below the threshold of $> 5\ \text{mg/L}$ required for Class 2 waters, indicating conditions of stress for aquatic life, and reached a critical minimum value of only $0.5\ \text{mg/L}$. Nutrient pollution is highly evident, as the mean concentration of Total Phosphorus ($4.8\ \text{mg/L}$) and Total Nitrogen ($26.2\ \text{mg/L}$) drastically surpassed the established limits of $0.1\ \text{mg/L}$ and $2.18\ \text{mg/L}$ for all classes, respectively. Furthermore, the Biochemical Oxygen Demand (BOD) reached an average of $21.3\ \text{mg/L}$ and peaked at $73.4\ \text{mg/L}$, values far above the $5\ \text{mg/L}$ permitted for Class 2, signifying a substantial organic load. The most critical indicator of sanitary contamination is the mean of Thermotolerant Coliforms ($325,833.0\ \text{NMP/100mL}$), which exceeds the Class limits of $1,000$ to $4,000\ \text{NMP/100mL}$ by hundreds of times, confirming the discharge of raw sewage into the stream. Most of the other parameters (pH, Turbidity, and Total Solids) remained, on average, within or near the limits established for their respective Classes.