Desenvolvimento de um método analítico para determinação de DQO por espectroscopia UV-Vis e quimiometria

Abstract

With the advancement of process analytical chemistry and the demand for quick and no-conditioning sample analyses, new analytical methods have been developed with the aim of replacing classical ones, realized in laboratory. In this context, the objective of this study was to develop a simple and rapid method for quantifying the chemical oxygen demand (COD) using ultraviolet-visible spectroscopy (UV-Vis) combined with multivariate analysis. Regression models were obtained using samples of domestic effluents collected from seven sewage treatment plants operated by the Paraná Sanitation Company (Sanepar). A total of 289 samples were collected over approximately a year and a half. Through exploratory analysis using the principal component analysis (PCA) method, a certain separation trend among the samples was observed based on the type of treatment used in the effluents. Regression models were obtained using the partial least squares (PLS) method. The global model, developed using samples from all seven treatment plants, exhibited values of RMSEC, RMSECV, and RMSEP equal to 13.76, 14.07, and 15.14 mg/L O2, respectively. Local models were also developed, using samples from treatment plants with similar characteristics, but no significant improvement was observed in the RMSEC, RMSECV, and RMSEP values. Based on the results obtained, it can be concluded that the developed method allows for the simple and rapid determination of COD in treated domestic effluents. The analyses can be performed directly, without the need for any sample preparation steps, and consequently, without generating waste. Therefore, this method can be applied in online or in-line process analyzers, as well as in portable analyzers.