Lipophilic wood extractives abatement from TMP circulation waters by wet oxidation

• Published in: Advances in environmental research : an international journal of research in environmental science, engineering and technology Vol. 8; no. 3; pp. 293 - 301
• Main Authors: Verenich, S., Garcia Molina, V., Kallas, J.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2004
• Subjects: Lipophilic wood extractives; pH influence; TMP circulation water; Wastewater treatment; Wet Oxidation; Lipophilic wood extractives; Wastewater treatment; TMP circulation water; Wet Oxidation; pH influence
• ISSN: 1093-0191; 1093-7927
• DOI: 10.1016/S1093-0191(02)00104-1

The closure of the internal water cycles in plants has lead to an increase in the demand for additional treatment processes of water effluents in order to degrade dissolved and colloid substances that have accumulated. Lipophilic wood extractives (LWEs) belong to this group of substances. This paper studied the wet oxidation (WO) of paper mill effluents with the aim of degrading LWEs. The experiments were performed at various temperatures (120–170 °C), partial oxygen pressures (0.5–1.5 MPa) and pHs (2, 5.5 and 12–13) in a batch stainless-steel high-pressure autoclave. The model of concentrated thermomechanical pulp circulation water was selected for the experiments. Each extractive group, such as resin acids, fatty acids, lignans, sterols, steryl esters and triglycerides, reacted with oxygen at a different rate, and the experiments showed that the more complete degradation of LWEs at the original pH would be possible at an oxygen partial pressure of 1 MPa and temperatures above 150 °C. Decreasing or increasing the pH of a wastewater sample to 2 or 13, respectively brought about a degradation of LWEs by 95–97% at 130 °C. Alkali treatment at 130 °C resulted in the increase of biodegradability to 75%. A lumped kinetic model was used in order to predict the changing concentration of LWEs during WO. This model, along with the concentration of LWEs, was able to predict the reaction selectivity and the biodegradability of wastewater. The model correlated well with the experimental data. The activation energies and reaction orders for each extractive group were determined using simplified kinetics.