Continuous Cr(VI) removal by Scenedesmus incrassatulus in an airlift photobioreactor
Carlos Rodrigo Jácome-Pilco
, Eliseo Cristiani-Urbina
, Luis Bernardo Flores-Cotera
, Teresa Ponce-Noyola
, Rosa Olivia Cañizares-Villanueva
Department of Biotechnology and Bioengineering, Cinvestav, Ave. IPN 2508, Col. San Pedro Zacatenco, México 07360, DF, Mexico
Department of Biochemical Engineering, Instituto Politécnico Nacional – ENCB-IPN, Prol. de Carpio, Col. Plutarco Elías Calles, México 11340, DF, Mexico
Laboratorio de Osmorregulación, FES Iztacala, UNAM, Av. de los Barrios, Tlalnepantla 54090, Estado de México, Mexico
Received 16 January 2008
Received in revised form 23 October 2008
Accepted 25 October 2008
Available online 25 December 2008
Cr(VI) removal by Scenedesmus incrassatulus was characterized in a continuous culture system using a split-
cylinder internal-loop airlift photobioreactor fed continuously with a synthetic efﬂuent containing 1.0 mg
at dilution rate (D) of 0.3 d
. At steady state, there was a small increase (6%) on the dry biomass
(DB) concentration of Cr(VI)-treated cultures compared with the control culture. 1.0 mg Cr(VI) l
the photosynthetic pigments content and altered the cellular morphology, the gain in dry weight was not
affected. At steady state, Cr(VI) removal efﬁciency was 43.5 ± 1.0% and Cr(VI) uptake was 1.7 ± 0.1 mg
DB. The system reached a speciﬁc metal removal rate of 458
g Cr(VI) g
, and a volumet-
ric removal rate of 132
g Cr(VI) l
Ó 2008 Elsevier Ltd. All rights reserved.
Heavy metals, such as cadmium, copper, chromium, lead, silver,
nickel, mercury, uranium, selenium, and zinc, occurring in domes-
tic and industrial wastewaters cause severe changes in aquatic sys-
tems and living organisms when they are discharged into natural
water bodies. Their tendency to bioaccumulate, toxicity, carcino-
genic and mutagenic effects are well known (Ahalya et al., 2005).
Chromium occupies the seventh place among the most abundant
heavy metals in the planet (Katz and Salem, 1994). In natural aque-
ous environments, chromium occurs as the trivalent Cr(III) or
otherwise as the more toxic hexavalent form Cr(VI) which at pH
>6.4 it occurs as CrO
a most soluble, mobile and bioavailable
form, thus representing a greater risk to health as a consequence
of its known carcinogenic activity (Cervantes et al., 2001; Ahalya
et al., 2005).
Cr(VI) is discharged to water bodies from a variety of industrial
processes such as leather tanning, galvanic industry, catalyst, pig-
ments, and electroplating (Baral et al., 2006). Although, physical–
chemical processes have been generally utilized in industry to
remove Cr(VI)-ions from wastewaters, these processes have certain
drawbacks, namely high cost, and they are ineffective when the
initial heavy metal concentrations are lower than 100 mg/l
(Cabatingan et al., 2001). According to Rai et al. (2005), biological
methods involving biosorption/bioaccumulation to remove low
concentrations of Cr(VI) from aqueous systems could be an attrac-
tive alternative technology.
Heavy metal removal from aqueous solutions using inert or liv-
ing cells of different microalgae strains has been studied in sus-
pended and immobilized batch cultures (Mehta and Gaur, 2005;
Vannela and Verma, 2006), as well as their toxic effects (Pinto
et al., 2003; Horcsik et al., 2006). However, with exception of the
use of inert algal biomass as a biosorbent, e.g. AlgaSORB
et al., 2000), large scale application of microalgae for metal re-
moval has been limited.
Pulz (2001), Chen et al. (2005), and Carvalho et al. (2006),
among others, have pointed out the advantages of continuous cul-
ture systems and the use of photobioreactors (PBR) for microalgae
culture. Nevertheless, very few reports have been published re-
lated to the use of continuous microalgal cultures for heavy metal
removal (Aoyama and Okamura, 1993; Peña-Castro et al., 2004;
Muñoz et al., 2006).
In this work, we characterized the Cr(VI) removal by the chloro-
phyceae microalga Scenedesmus incrassatulus continuously culti-
vated in a split-cylinder internal-loop airlift photobioreactor at a
constant dilution rate.
2.1. Microorganism and growth conditions
The microalga S. incrassatulus (Chlorophyceae) CLHE-Si01
was obtained from the culture collection of the Experimental
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* Corresponding author. Tel.: +52 55 57473800x4342; fax: +52 55 57473313.
E-mail address: email@example.com (R.O. Cañizares-Villanueva).
Bioresource Technology 100 (2009) 2388–2391
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