Evaluation of the chemical oxigen demand of agriculture-industrial wastewaters by the spectrophotometric method using concentrated reagent.

The method for the determination of the Chemical Oxygen Demand, COD, has been modified to diminish reagent consumption, improve the accuracy of the end point detection and the time spent for the analysis. The spectrophotometric test determines the color of Cr+3 species when the sample is digested with sulfuric acid in the presence of potassium dichromate. In this study it was possible to define an analytical range of application between 80 - 3000 mg COD.l-1 and to modify substantially the reaction time. The use of the spectrophotometric method has some advantages in comparison with the titrimetric method recommended by American Public Health Association (1985) for the Examination of Water and Wastewater.

Key words: agricultural industry, wastewater, pollution, COD, colorimetry.