Characterization of Effluents Generated During the Cleaning of Expansion Tanks Used to Store Raw Milk in Brazil / Caracterização dos Efluentes Gerados Durante a Limpeza dos Tanques de Expansão Usados para Armazenar Leite Cru no Brasil

Abstract

The objective of this study was to characterize the effluents generated during the cleaning of the expansion tanks used to store raw milk in Brazil. Fifteen expansion tanks were chosen and three samples collected from each tank, as well as measuring the temperature and volume. The biological oxygen demand (BOD), chemical oxygen demand (COD), acidity, pH, alkalinity, total phosphorus, nitrogen, fats and oils, hardness, turbidity and total dissolved solids were determined. The statistical design adopted was completely at random and the Scott-Knott test was adopted to compare the means that differed significantly according to the F test. The multivariate data analysis was also carried out and studied by the principal component analysis (PCA) and the grouping analysis for similarity, as represented by a dendogram. The effluents were not treated and some of them (26.7%) were discharged into water courses. The concentrations of the organic matter indicators and the results of the physicochemical analyses of the expansion tank washing effluents showed that the majority of the variables were above the legal standards established by Brazilian legislation. Thus an adequate destiny for these effluents is required. The PCA showed that the variables with the greatest influence on the characteristics of the expansion tank effluents were related to the COD and nitrogen concentrations. A total of 88% of similarity was found between the effluents of the 15 tanks. According to the concentrations obtained for the phosphorus, nitrogen, COD and BOD of the effluents, they could be treated by the wetlands systems.The objective of this study was to characterize the effluents generated during the cleaning of the expansion tanks used to store raw milk in Brazil. Fifteen expansion tanks were chosen and three samples collected from each tank, as well as measuring the temperature and volume. The biological oxygen demand (BOD), chemical oxygen demand (COD), acidity, pH, alkalinity, total phosphorus, nitrogen, fats and oils, hardness, turbidity and total dissolved solids were determined. The statistical design adopted was completely at random and the Scott-Knott test was adopted to compare the means that differed significantly according to the F test. The multivariate data analysis was also carried out and studied by the principal component analysis (PCA) and the grouping analysis for similarity, as represented by a dendogram. The effluents were not treated and some of them (26.7%) were discharged into water courses. The concentrations of the organic matter indicators and the results of the physicochemical analyses of the expansion tank washing effluents showed that the majority of the variables were above the legal standards established by Brazilian legislation. Thus an adequate destiny for these effluents is required. The PCA showed that the variables with the greatest influence on the characteristics of the expansion tank effluents were related to the COD and nitrogen concentrations. A total of 88% of similarity was found between the effluents of the 15 tanks. According to the concentrations obtained for the phosphorus, nitrogen, COD and BOD of the effluents, they could be treated by the wetlands systems