MONITORAMENTO E RELACIONAMENTO DOS PARÂMETROS DQO E DBO5 EM AFLUENTE E ESGOTO TRATADO DAS CIDADES DE ITAJUBÁ E PEDRALVA, MG.

One of the main characteristics evaluated in municipal sewage treatment is the organic matter content, usually based on the analysis of Chemical and Biochemical Oxygen Demands, COD, and BOD respectively. The objective of this work was to analyze and compare the relation between the COD and BOD parameters for raw sewage (effluent) and treated sewage of two wastewater treatment plants (WWTPs) of the cities of Itajubá and Pedralva, both localized in the south of Minas Gerais, Brazil. Due to the data obtained over two years from the state sanitation company, the analysis of ratios and linear correlation between COD and BOD5 were performed, as well as their removal (%) to verify the WWTP efficiencies. The COD/BOD5 value of 2.13 was obtained for the affluent of Itajubá city, while for Pedralva was 2.20. These values are common at the typical range of raw domestic wastewater, and no evidence of industrial contribution was found. The values of the linear correlation coefficient (R²) between the COD and BOD5 parameters for affluent of Itajubá and Pedralva were 0.8585 and 0.4863, respectively, suggesting that BOD5 value can be estimated from COD only in the first case (R²>0.8). For treated sewage samples from both WWTPs, this approach is not appropriate because the R² values were lower than 0.3. According to current state legislation (COPAM/CERH nº 01), the two WWTPs efficiently removed the BOD5, while Itajubá WWTP showed COD removal slightly below the stipulated. Following federal legislation (CONAMA nº 430), both WWTPs have efficiently removed BOD5. [ABSTRACT FROM AUTHOR]