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The effectiveness of a biological treatment with Rhizopus
oryzae and of a photo-Fenton oxidation in the mitigation of
toxicity of a bleached kraft pulp mill effluent
R. Pereiraa,*, S.C. Antunesa, A.M.M. Gonc¸alvesb, S.M. Marquesa, F. Gonc¸alvesa, F. Ferreirac,
A.C. Freitasc, T.A.P. Rocha-Santosc, M.S. Dinizd, L. Castrod, I. Peresd, A.C. Duartee
aCESAM (Centro de Estudos do Ambiente e do Mar) & Departamento de Biologia, Universidade de Aveiro, Campus de Santiago, 3810-193
Aveiro, Portugal
bIMAR-CIC – Centro Interdisciplinar de Coimbra, Departamento de Zoologia da Universidade de Coimbra, 3004-517 Coimbra, Portugal
cISEIT/Viseu, Instituto Piaget, Estrada do Alto do Gaio, Galifonge, 3515-776 Lordosa, Viseu, Portugal
dIMAR – Instituto do Mar, Faculdade de Cieˆncias e Tecnologia da Universidade Nova de Lisboa, Departamento de Cieˆncias e Engenharia do
Ambiente, Quinta da Torre 2829-516, Portugal
eCESAM (Centro de Estudos do Ambiente e do Mar) & Departamento de Quı´mica, Universidade de Aveiro, Campus de Santiago, 3810-193
Aveiro, Portugal
a r t i c l e i n f o
Article history:
Received 29 October 2008
Received in revised form
3 March 2009
Accepted 9 March 2009
Published online 18 March 2009
Keywords:
Bleached kraft pulp mill effluent
Photo-Fenton oxidation
Rhizopus oryzae treatment
Toxicity assays
Freshwater species
a b s t r a c t
Huge efforts have been made both in adopting more environmental-friendly bleaching
processes, and in developing advanced oxidation processes and more effective biological
treatments for the reduction of deleterious impacts of paper mill effluents. Even so, the
success of such treatments is frequently reported in terms of chemical parameters without
a proper evaluation of the effluent’s toxicity mitigation. This is the first study reporting an
exhaustive evaluation of the toxicity of a secondary bleached kraft pulp mill effluent, after
either tertiary treatment with the soft-rot fungi Rhizopus oryzae or with a photo-Fenton
oxidation, using a battery of freshwater species. As it has been reported the photo-Fenton/
UV treatment has proved to be the most effective in reducing the colour and the COD
(chemical oxygen demand) of the effluent. Nevertheless, extremely low EC50 values were
reported for almost all species, after this tertiary treatment. The treatment with R. oryzae
was less effective in terms of colour removal and COD reduction, but proved to be the most
promising in reducing toxicity.
ª 2009 Elsevier Ltd. All rights reserved.
1. Introduction
The reduction in COD, BOD (chemical and biochemical oxygen
demand), colour and toxicity of industrial effluents is an
important issue when evaluating the effectiveness of new
developed treatment methodologies. In the paper and pulp
industry the conventional wood pulping is usually performed
by a chemical process (Kraft), that removes cellulose from
wood dissolving lignin, which is followed by bleaching to
remove chromophores (USEPA, 2002). This bleaching process
has been reported as mainly responsible for the toxicity of
resulting wastewaters, mainly due to chloro-organic deriva-
tives resulting from the use of chlorine, chlorine dioxide or
hypochlorite, which are the primary causative agents of
adverse effects on aquatic biota from receiving systems
(Brunner and Pullian, 1993; Felder et al., 1998; Yeber et al.,
* Corresponding author. Tel.: þ351 234 370 788; fax: þ351 234 372 587.
E-mail address: ruthp@ua.pt (R. Pereira).
Avai lab le a t www.sc iencedi rec t .com
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0043-1354/$ – see front matter ª 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.watres.2009.03.013
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