Tema Bioprocesos

Bioprocess Biosyst Eng (2008) 31:535–540 DOI 10.1007/s00449-007-0194-0

ORIGINAL PAPER

Anaerobic treatment of low-strength synthetic TCF effluents and biomass adhesion in fixed-bed systems
Anuska Mosquera-Corral Æ Angela Belmar Æ Jacqueline Decap Æ Katherine Sossa Æ Homero Urrutia Æ Gladys Vidal

Received: 13 November 2007 / Accepted: 21 December 2007 / Published online: 12 January 2008 ÓSpringer-Verlag 2008

Abstract Toxicity effects produced by kraft mill effluents are due to the productive process. New bleaching processes have been proposed (e.g. total chlorine free, TCF) to reduce the production of toxic chlorine compounds. In the TCF processes large amounts of chelating compounds like the ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DPTA) areused. The aim of this work is to research the feasibility of the degradation of low-strength synthetic TCF effluents in a anaerobic filter reactor (AF) and the biomass adhesion. The effects on the operation of the AF at different EDTA loading rates were tested in the range from 0.07 to 0.51 g EDTA l-1 days-1. The maximum EDTA removal percentage achieved was of 27%. Acute toxicity (measured as 24h-LC50) with Daphnia magna was reduced from 14.23 to 54.53% before and after anaerobic treatment, respectively. Observations of biomass samples from the AF under the scanning microscope verified the attached biomass.

Keywords Anaerobic Á Biomass adhesion Á Ethylenediaminetetraacetic acid (EDTA) Á Total chlorine free (TCF) effluent

Introduction In recent years, important technological innovationshave been developed worldwide in the forest industry, aimed at reducing water consumption and generation of toxic contaminants. Thus, water circuit closures, new pulping and bleaching processes have been introduced in order to reduce water consumption and production of chlorinated phenolic compounds. The TCF (total chlorine free) bleaching process is one of these processes, which aims tocompletely remove the discharges of chlorinated compounds [1]. Furthermore, it has been stated that TCF bleaching enhances the anaerobic COD biodegradability of the effluent generated up to 75% [2]. However, the introduction of this TCF pulp is associated to an increment on the amounts of chelating compounds used to remove the metals present in the obtained cellulose pulp [3]. The most commonly usedchelating compounds are ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DPTA) [4]. No studies have been completed within the pulping industry that demonstrates the feasibility of removal of these chelating compounds by anaerobic biological treatment. In some cases after a chemical oxidation it has been observed the aerobic degradation of both compounds [3]. Furthermore,the recalcitrant properties of the DPTA have been already studied [5]. EDTA has been also used to decrease the inhibitory effects on the methanogenic activity of metals like cadmium, copper, nickel [6, 7]. All this factors make it interesting the study of these compounds in the anaerobic processes.

A. Mosquera-Corral Department of Chemical Engineering, School of Engineering, University ofSantiago de Compostela, ´ Lope Gomez de Marzoa s/n, 15782 Santiago de Compostela, Spain A. Belmar Á J. Decap Á G. Vidal (&) Environmental Science Center EULA-Chile, ´ ´ University of Concepcion, P.O. Box 160-C, Concepcion, Chile e-mail: glvidal@udec.cl K. Sossa Á H. Urrutia ´ Biotechnology Center, University of Concepcion, ´ P.O. Box 160-C, Concepcion, Chile

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Bioprocess Biosyst Eng(2008) 31:535–540

In the half 60 s the anaerobic digestion was established as an alternative to treat effluents with high organic loads (1– 40 g COD l-1 days-1), but also for low-strength (\1 g COD l-1 days-1). It was in the early 90 s when these technologies were extensively applied to the forest industry [8]. The use of these technologies allows the production of effluents which can be reused in...