Décoloration des eaux usées de levurerie par adsorption sur charbon

Abstract

The decolorization study of a yeast wastewater factory by adsorption on activated and raw charcoal showed that these adsorbents have great capacity to discolor and to adsorb the total organic matter (TOM), the chemical oxygen demand (COD), and the dissolved organic carbon (DOC). The solutions color characteristics have been followed by determining their dominant wavelengths issued from their correspondent trichromatic coefficients (X,Y,Z). The adsorbent size is an important parameter. The use of 30 g of charcoal sized 150–250 µm, per liter of solution, leads to a total decolorization, and to a diminution of up to 50% of the treated solutions COD and DOC concentrations. To obtain the same efficiency, 130 g/L of 425- to 850-µm sized charcoal are needed. The study of the kinetics of the discoloration shows that the adsorbent instantly reaches a saturated state with a saturation rate almost equivalent to the rate of its diffusion in the liquid. It shows also that the maximum amounts of the adsorption of the COD and the DOC can be modelled by the Langmuir adsorption isotherm, and that they are respectively equal to 231 and 213 mg/g for the nonactivated charcoal (150–250 µm), and 103 mg/g for the activated charcoal (425–850 µm) regarding the COD, and that the Freundlich adsorption model fit well the COD and DOC adsorption for the nonactivated charcoal. Key words: decolorization, charcoal, adsorption, yeast, wastewater.