Distribution of absorbance in the visible spectrum related to molecular size fractions in secondary and tertiary municipal-textile effluent

Abstract

Distribution of absorbance into the visible spectrum was investigated as a function of the molecular size in the following streams: the secondary effluent from a denitrification/nitrification activated sludge treatment plant (80% as COD load and 70% as hydraulic load from textile industries) and the intermediate and final effluents of a pilot-scale advanced wastewater treatment (AWT) fed on the secondary effluent, consisting of clariflocculation (FPS) and of granular activated carbon adsorption (GAC). Correlations with the TOC distribution determined in a previous research were also investigated. The TOC distribution and absorption fingerprints as a function of the molecular “cuts” were found to be quite different: TOC was made of small fractions up to the last “cut” for the three sampled streams (influent, effluent FPS and effluent GAC). The % absorbance distribution is much less homogeneous, and correlation between %TOC and % absorbance seem to be very poor which confirms that photometric analysis in the visible spectrum is unsuitable to monitor residual pollution in textile effluents.