Characteristics of dissolved organic material in total chlorine free bleach plant and laboratory effluents

Abstract

The dissolved organic material present in totally chlorine free (TCF) pulp mill bleaching effluents and in their laboratory made counterparts was characterized using chemical and chromatographic analysis. Special attention was given to analysis of material originating from lignin and carbohydrate. With the exception of the P 2 laboratory effluent, the BOD 7 , COD and TOC loads and the content of aromatic lignin in the effluents, were higher in the mill effluents. After oxygen stages, the content of monomeric acidic phenols and aromatic acids in the effluents was very low. The highest amount of carbohydrates was found dissolved in the first P stage mill effluent. The average molar mass of UV-absorbing material was lowest in ozone effluents. Carbohydrates were determined as monosaccharides after acid hydrolysis. Xylan was the main carbohydrate component in most effluents, and after ultrafiltration more xylose was found in fractions over 10 000 NMM. Ozone effluents were rich in arabinose, which was mostly found in fractions below 10 000 NMM. Most of the mannose and galactose that dissolved in the first alkaline peroxide stage effluents was found in fractions over 10 000 NMM.