REVIEWARTICLE
Valorization of solid waste products from olive oil industry
as potential adsorbents for water pollution control—a review
Amit Bhatnagar & Fabio Kaczala & William Hogland &
Marcia Marques & Christakis A. Paraskeva &
Vagelis G. Papadakis & Mika Sillanpää
Received: 1 May 2013 /Accepted: 5 September 2013 /Published online: 26 September 2013
# Springer-Verlag Berlin Heidelberg 2013
Abstract The global olive oil production for 2010 is estimated
to be 2,881,500 metric tons. The European Union countries
produce 78.5%of the total olive oil, which stands for an average
production of 2,136,000 tons. The worldwide consumption of
olive oil increased of 78 % between 1990 and 2010. The
increase in olive oil production implies a proportional increase
in olive mill wastes. As a consequence of such increasing trend,
olivemills are facing severe environmental problems due to lack
of feasible and/or cost-effective solutions to olive-mill waste
management. Therefore, immediate attention is required to find
a proper way of management to deal with olive mill waste
materials in order to minimize environmental pollution and
associated health risks. One of the interesting uses of solid
wastes generated from olive mills is to convert them as inexpensive
adsorbents for water pollution control. In this review
paper, an extensive list of adsorbents (prepared by utilizing
different types of olive mill solid waste materials) from vast
literature has been compiled, and their adsorption capacities for
various aquatic pollutants removal are presented. Different physicochemical
methods that have been used to convert olive mill
solid wastes into efficient adsorbents have also been discussed.
Characterization of olive-based adsorbents and adsorption
mechanisms of various aquatic pollutants on these developed
olive-based adsorbents have also been discussed in detail.
Conclusions have been drawn from the literature reviewed,
and suggestions for future research are proposed.
Keywords Olivemill . Solidwaste products . Valorization .
Adsorbents . Water treatment
Introduction
The increasing worldwide contamination of freshwater systems
with industrial and natural chemical compounds is one of
the key environmental problems (Schwarzenbach et al. 2006).
About one fifth of the world's population does not have access
to safe water, and two fifths suffer the consequences of unacceptable
sanitary conditions (UNESCO 2003). Intensive research
on effective water treatment has resulted in several
technologies, which have been employed with varying degree
of success for the removal of toxic pollutants from water
and wastewater. Among various water treatment technologies,
“adsorption” process is considered as one of the best
methods available for the removal of diverse types of
Responsible editor: Bingcai Pan
A. Bhatnagar (*) : F. Kaczala :W. Hogland :M. Marques
Department of Biology and Environmental Science,
Faculty of Health and Life Sciences, Linnaeus University,
391 82 Kalmar, Sweden
e-mail: amit.bhatnagar@lnu.se
A. Bhatnagar
e-mail: dr.amit10@gmail.com
M. Marques
Department of Sanitary and Environmental Engineering,
Rio de Janeiro State University, UERJ, Rio de Janeiro, Brazil
C. A. Paraskeva
Institute of Chemical Engineering Sciences, Foundation for Research
and Technology, Hellas (FORTH/ICE-HT), Stadiou Street, Platani,
Patras 26504, Greece
C. A. Paraskeva
Department of Chemical Engineering, University of Patras,
26504 Rion, Patras, Greece
V. G. Papadakis
Department of Environmental & Natural Resources Management,
University of Patras, 30100 Agrinio, Greece
M. Sillanpää
Faculty of Technology, Lappeenranta University of Technology,
Laboratory of Green Chemistry, Sammonkatu 12, 50130 Mikkeli,
Finland
Environ Sci Pollut Res (2014) 21:268–298
DOI 10.1007/s11356-013-2135-6
pollutants from water and wastewater. Various conventional
and nonconventional adsorbents have been used for their
suitability towards water remediation (Bhatnagar 2012). From
last few decades, research has been directed towards developing
low-cost adsorbents utilizing naturally occurring and agroindustrial
waste materials as these materials are cheaper, renewable,
and abundantly available. Various review articles
have been published in recent years where the potential of
these adsorbents have been reviewed (Ahmad et al. 2012;
Bhatnagar and Sillanpää 2010; 2009; Bhatnagar et al. 2010;
Chuah et al. 2005; Crini 2006; Zhou and Haynes 2010).
Special focus is now being given to utilize solid industrial
wastes (by-products), which sometimes pose serious disposal
problems. Olive oil industry is one such industry that produces
enormous amount of solid and liquid wastes, and these wastes
cause serious environmental problems.
Today, over 10 million ha area worldwide is covered by
about 900 million olive trees, 98% of which are located in the
Mediterranean Basin (Sesli and Yeğenoğlu 2009), covering an
area of 5,163,000 ha, while deriving >93 % of the total olive
oil produced. The global olive oil production for 2010 is
estimated to be 2,881,500 metric tons (Stamatakis 2010).
The European Union countries produce the 78.5 % of total
olive oil which stands for an average production of
2,136,000 tons (Stamatakis 2010). The largest oliveproducing
country is Spain with 1,200,000 tons followed by
Italy with 540,000 tons, Greece with 348,000 tons, Portugal
with 50,000 tons, and finally, France and Cyprus with
5,000 tons (Stamatakis 2010). Other non-EU-Mediterranean
olive-producing countries are Tunisia with 185,000 tons,
Syria with 128,000 tons, Turkey with 117,000 tons, and
Morocco with 78,300 tons (IOC 2010; Niaounakis and
Halvadakis 2006). Each olive tree produces 15–40 kg of
olives/year depending on the climate conditions. The chemical
composition of olives, which is the raw material for olive
oil extraction, is very variable and depends on several factors
such as, the olive variety, soil type, and climatic conditions,
but in general, it consists of 18–28 % oil, 40–50 % vegetation
water and stone, and 30–35 % of olive pulp (Niaounakis and
Halvadakis 2006). In the last decade, olive oil production has
increased by approximately 40 % worldwide. The olive tree
yield is greatly affected by a biennial cycle: one year it grows,
and the other year gives more fruits. Therefore, more olive oil
and wastes are generated every other year (Azbar et al. 2004;
Boskou 2006).
Olive oil extraction is the process of separating and
collecting the oil from the olives. The main processing steps
needed to obtain olive oil include: feeding, leaf removal and
washing, crushing, mixing, separating the olive oil, and
centrifuging the oil. Today, three different extraction processes
are commonly used: (1) The traditional process, (2) the twophase
decanter process, and (3) the three-phase decanter process.
In the traditional press process, the olives are washed,
crushed, and kneaded with the addition of warm water
(∼38 °C). The resulting paste is then pressed to drain the oil,
and the liquid waste originating from presses consists of a
mixture of olive juice and added water and contains residual
oil. Finally, olive oil is separated from the water by vertical
centrifugation or decanting (Azbar et al. 2004). The use of the
traditional process has decreased, and nowadays, it is almost
only employed in small olive mills. The continuous system
can be operated by three- and two-phase extraction technologies,
diverging in the water supplies. While the two-phase
system does not require the addition of water, producing olive
oil and olive cake, the three-phase demands the addition of hot
water to the decanter, producing olive oil, olive mill wastewater
(OMW), and olive cake (residual solids). As a result of
these differences, the three-phase extraction process has a
slightly better yield, leading to less amount of olive cake but
a significant production of olive mill wastewater (Paraskeva
et al. 2007a,b; Roig et al. 2006). The traditional cold press
method typically generates about 50 % of OMW, relative to
the initial weight of the olives, while the continuous centrifugation
process generates (80–110)% of OMW (Mantzavinos
and Kalogerakis 2005). The advantages and disadvantages of
each method, as well as other details, can be found elsewhere
(Borja et al. 2006; Boskou 2006; Niaounakis and Halvadakis
2006).
To release most of the oil present in the olive during
processing, water is used in various steps e.g., in washing,
mixing (when olives are entirely dry) and diluting the paste,
and in the final separation of the olive oil where the olive oil is
purified.Water used in these stages corresponds to 10, 40, and
20 % out of the initial olive weight, respectively. To show the
mass yield, 1 kg of olive oil is produced after the processing of
approximately 5 kg of olives. The composition of the waste
streams is not constant qualitatively or quantitatively, and it
varies according to soil cultivation, harvesting time, degree of
ripening, olive variety, climatic conditions, use of pesticides
and fertilizers, and duration of aging (Niaounakis and
Halvadakis 2006). In general, during the two-phase olive
extraction process, olive mill waste consists of about 44 %
of solid wastes and 56 % of liquid waste (Ayrilmis and
Buyuksari 2010). Three-phase oil extraction procedure results
in the production of ∼20 % of olive oil per kilogram
of treated olive fruits and both solid and liquid wastes.
OMW are acidic, have extremely high biological oxygen
demand (BOD) and chemical oxygen demand (COD)
values (100–150 g/L), and also contain toxic levels of
polyphenols (Azbar et al. 2004; Paraskeva et al. 2007a,b;
Paraskeva and Diamadopoulos 2006).
According to the facts of International Olive Council, the
worldwide consumption of olive oil increased of 78 % between
1990 and 2010. The increase in olive oil production
implies a proportional increase in olivemillwastes. It has been
estimated that the annual world olive oil production yields
Environ