Vol.3, No.5, 371-378 (2011) Natural Science
http://dx.doi.org/10.4236/ns.2011.35050
Comparative study of thermophilic and mesophilic
anaerobic treatment of purified terephthalic
acid (PTA) wastewater
Michael Olawale Daramola1*, Elizabeth Funmilayo Aransiola1, Adeniyi Ganiyu Adeogun2
1Department of Chemical Engineering, Obafemi Awolowo University, Ile-Ife, Nigeria; *Corresponding Author:
2Department of Integrated Urban Engineering, UNESCO-IHE Institute of Water Education, Delft, The Netherlands.
Received 11 February 2011; revised 5 March 2011; accepted 27 March 2011.
ABSTRACT
The paper provides a critical comparison be-
tween mesophilic and thermophilic anaerobic
treatment of PTA wastewater through diagnosis
of a case study. Aspects covered are bioavail-
ability, biodegradability, microbial population,
thermodynamics, kinetics involved and bio-
reactor design for PTA wastewater treatment.
The results of the case study suggests that one-
stage thermophilic anaerobic reactor coupled
with coagulation-flocculation pre-treatment unit
and an aerobic post treatment unit could be
techno-economically viable for PTA wastewater
treatment to ensure that the final effluent quality
conforms to the international standard. The in-
formation emanated from this study could be
useful and thought provoking to the profes-
sionals and academia in the area of PTA waste-
water treatment and can serve as impetus to-
ward the development of research lines in similar
problems like the treatment of other petro-
chemical wastewater such as phenol-containing
wastewater, benzene/benzoic acid-containing
wastewater or wastewater from other similar in-
dustrial settings.
Keywords: Terephthalic Acid; Wastewater
Treatment; Anaerobic and Aerobic Treatment;
Mesophilic and Thermophilic Conditions;
Bioreactors
1. INTRODUCTION
In 1997, worldwide production of purified terephthal-
ic acid (PTA) was 18.22 million tons and it grew steadily
to about 26.12 million tons in 2002 at an annual growth
rate of 7.5% with China growth rate accounted for about
2.6 million tons. In 2005, the demand for PTA in China
rose up to 12.14 million tons contributing to 42% of the
total world demand of about 28.8 million tones [1,2].
The process for the production of PTA developed by
the American Amoco Group [3] comprises:
 Wet oxidation of p-Xylene into acetic acid to pro-
duce crude terephthalic acid (CTA).
 Hydrogenation of CTA into PTA over palladium as
a catalyst [4].
During the process, about 4 - 10 kg COD·m−3 are
generated with 5 - 20 COD·L−1, and 3 - 4 m3 wastewater
per ton of PTA generated [5]. Significant part of PTA
wastewater consists of p-toluic acid (p-Tol), benzoic acid
(BA), 4-carboxybenzaldehyde (4-CBA), phthalic acid
(PA) and terephthalic acid (TA) with minor concentra-
tions of 4-formylbenzoic acid, methyl acetate and p-
xylene [6-8]. At times, the contribution of these chemi-
cals towards COD can be more than 75% in the waste-
water. With increasing PET consumption, the treatment
of PTA wastewater and contaminated environments is
very essential to preserve natural ecosystems and protect
the environment because untreated PTA waste water
released into the environment is toxic to living organ-
isms [9-12]. Acute toxicity, sub-acute toxicity, chronic
toxicity and molecular toxicity have been reported for
exposure to pure chemical PTA [11,13-16].
Additionally, phthalate, its ester and degradation in-
termediates are suspected to cause cancer and renal
damage, and as a result of this, the US Environmental
Protection Agency has recently added this class of
chemicals to the list of priority pollutants [17]. The toxic
concentrations or doses of the pure chemical PTA were
as high as over 1000 mg·L−1. Several methods such as,
advanced oxidation processes (AOP), supercritical water
oxidation, UV-assisted ozonation (UV/O3), ozone as-
sisted photochemical oxidation (UV/O3/H2O2), pho-
to-fenton oxidation(UV/H2O2/FeSO4), ozone-assisted pho-

M. O. Daramola et al. / Natural Science 3 (2011) 371-378 372
to-fenton oxidation (UV/O3/H2O2/FeSO4) and radiation
treatment using gamma-ray have been used for the
treatment of PTA wastewater [18-21]. However, cost for
treatment and generation of toxic intermediates and
sludge, which in turn cause secondary pollution, have
been identified as major limitations of these methods. To
overcome these limitations, biodegradation technology
has been proposed and used.
Biodegradation or biological treatment has been found
to be environmental friendly and cost effective and in
some cases, energy-efficient compared to chemical pro-
cesses. However in biodegradation, poor degradation of
the intermediate poses a problem [22-24]. Nevertheless,
this problem does not pose serious hindrance to the ap-
plication of biodegradation to wastewater treatment.
Regarding the application of biodegradation technology
for PTA wastewater treatment, activated sludge process
(aerobic treatment) has been proposed and used [23].
Advantages of aerobic treatment are high purification
efficiency (>90%), high process stability and rapid bio-
degradability of all compounds. Meanwhile, in recent
years, anaerobic treatment has been preferred to conven-
tional aerobic activated sludge treatment process due to
the reasons presented in Table 1.
In light of this, the objective of this paper is to present
a critical comparison between aerobic and anaerobic
degradation of PTA wastewater with a view to furnishing
the readers with useful information on PTA wastewater
treatment and provoking their thought toward the appli-
cation of the process to wastewater treatment from simi-
lar industrial settings. Furthermore, the comparison is
presented through the diagnosis of a scenario which
concerns a PTA wastewater containing terephthalate,
benzoate and acetate. The concentrations of the tere-
phthalate, benzoate and acetate in the waste stream are 3,
Table 1. Comparison between aerobic activated sludge and
anaerobic degradation of wastewater.
Aerobic activated sludge Anaerobic degradation
High energy intensive Low energy intensive
Large volume of sludge Small volume of sludge
Requires highly skilled
operation and process control
Requires moderate skilled
operation and process control
Additional nutrients is required No additional nutrients required
Costly technical specifications No costly technical specifications
Poor solid settleability Good solid settleabiblity
Requires high hydraulic
retention time (HRT) Low HRT
Low elimination rate High elimination rate
2 and 2 g·L−1, respectively. The wastewater leaves the
plant at a temperature of 54˚C - 60˚C and a pH of 5.
Thus this paper compares mesophilic and thermophilic
anaerobic degradation of the wastewater and suggests an
economically viable option for the treatment of the
wastewater. In the course of the diagnosis, issues like
bioavailability, biodegradability, microbial population,
kinetics and thermodynamics of anaerobic degradation
of PTA wastewater were considered and discussed.
2. BIOAVAILABILITY,
BIODEGRADABILITY AND
TOXICITY OF TA
Terephthalic acid is a benzene ring structure with two
carboxylic acid groups. These two acid groups are re-
sponsible for the high solubility of TA in water. It is
known that TA has a high solubility of about 140 g·L−1
at pH > 5.5 [25]. Therefore, bioavailability of TA for the
degrading bacteria is promising. However, the pH should
be > 5.5 or else precipitation of TA might occur. When
the pH < 5.5, TA precipitation occurs, and the TA will be
unavailable anymore for degradation. Kleerebezem et al.
[26] have proposed a two-step biodegradation pathway
for PTA wastewater. In this pathway, the first step in-
volves the decarboxylation of TA to form benzoate and
the second step involves the transformation of benzoate
to carboxycyclohexane. The two carboxylic acid groups
have a stabilizing effect on the benzene ring and make it,
therefore, not easy to degrade. In term of toxicity, TA has
not been found to be severely toxic to methanogens at
the usual concentration of TA present in PTA wastewater
[4,27,28]. Also, the partition coefficient (log OW
k) of TA
has been reported to be 1.16 to 2.00 (depending on
which isomer of TA and of the state of the isomer-dis-
sociated or non-dissociated) [28].
3. THERMODYNAMICS OF ANAEROBIC
DEGRADATION OF PTA
WASTEWATER
The main conversion reactions that occur during an-
aerobic treatment of PTA wastewater are TA decarboxy-
lation, benzoate oxidation, benzoate reduction, and/or
carbocyclohexane oxidation. Under the prevalent condi-
tions (pH, concentrations and temperature of the waste-
water), the TA decarboxylation can proceed but close to
the biological limit of –20 KJ·mol–1. The benzoate oxi-
dation, however, does not proceed under these condi-
tions. The only reaction that is probably promoted is the
TA carboxylation (but only for a limited time; until the
benzoate concentrations reached a high value). The ben-
zoate reduction proceeds because H2 that is needed for
the reaction must come from the benzoate oxidation,

M. O. Daramola et al. / Natural Science 3 (2011) 371-378 373
which cannot proceed under these conditions. At pH of 7,
however, all the reactions can proceed except the carbo-
cyclohexane reaction.
Furthermore, the TA decarboxylation reaction might
not proceed, because when the TA decarboxylation and
benzoate reduction and oxidation are carried out by the
same organism, benzoate reduction and oxidation path-
way is favoured. This occurs because those two reac-
tions deliver more energy than the TA decarboxylation.
Figure 1 and Figure 2 depict the different Gibbs free
energies for the reactions at the actual concentrations of
TA, benzoate and acetate at different pH, 37˚C and 55˚C,
respectively (The values of Gibbs free energy of forma-
tion of the compounds were taken from Reference [26]
and Reference [29]). Therefore, to remove the TA, the
benzoate and acetate concentrations should be low.
Comparing Figure 1 and Figure 2 shows that an in-
crease in temperature from 37˚C to 55˚C improves the
energy yield for almost all reactions except the benzoate
reduction (see Figure 2). This indicates that higher tem-
peratures are preferable for TA degradation. However,
Figure 1. Gibbs free energy for the different reactions at dif-
ferent pH at the actual concentrations of TA, Benzoate and
acetate at 37˚C.
Figure 2. Gibbs free energy for the different reactions at dif-
ferent pHs at the actual concentrations of TA, benzoate and
acetate at 55˚C.
Kleerebezem and Lettinga [30] reported unsuccessful
results on anaerobic degradation PTA wastewater at
thermophilic condition. The failure could be attributed to
the possibility of low number of thermophilic anaerobic
TA degrading microorganisms in the inoculum’s sludge
and/or non-optimal operating conditions during the TA
degradation. In the contrary, Chen et al. [31] reported
relatively high TA and benzoate removal in one reactor
at thermophilic condition compared to the removal at
mesophilic condition (0.7 versus 0.5 g TA/gVSS (day)−1).
Success of Chen et al. could be attributed to the different
TA biodegradation kinetics during thermophilic condi-
tion compared to the kinetics during mesophilic condi-
tion.
At higher temperatures, Gibbs free energies for TA
biodegradation are more negative. Thus favouring and
enhancing thermophilic PTA degradation. At the same
time, the pH should be taken into consideration. Consid-
ering the influence of pH, plots on Figures 1 and 2 are
only valid for a pH ≥ 5.5 because at pH < 5.5, TA is
mainly available in solid form [4]. Also, optimal growth
of the TA degrading organisms occurs in a range of pH 6
to 7 [4]. Therefore for feasible anaerobic degradation of
the PTA wastewater described in this study (the waste-
water has a pH = 5), the pH of the wastewater should be
increased to 6 or 7 by adding alkali. In the optimal pH
growth range, the benzoate oxidation and reduction gain
more energy than the TA decarboxylation. Also, it is
likely that only TA decarboxylation will proceed if the
benzoate concentration is low as suggested by Kleere-
bezem et al. [26]. The hypothesis of Kleerebezem et al.
[26] was verified in this study through computations.
Based on these computations, we concluded that anaero-
bic degradation of the wastewater (our case study) is
possible and feasible under both mesophilic and thermo-
philic conditions. However, in a case where the pH of the
wastewater ≤ 5, during the treatment the pH of the
sludge should be increased to 7 (the optimum pH for the
anaerobic treatment [30]). Addition of appropriate
amount of chemicals such as sodium hydroxide solution
(NaOH) sodium bicarbonate (NaHCO3) to the wastewa-
ter bioreactor could raise the pH to 7.
4. MICROBIAL POPULATION FOR
ANAEROBIC DEGRADATION OF
PTA WASTEWATER
Identification of structure and diversity of a microbial
community is important in degradation processes be-
cause it is useful for better understanding of the physio-
logical roles of different species in degradation proc-
esses. Different types of bacteria have different roles
under different conditions. Like in thermophilic and me-
sophilic conditions, microbial community that will be

M. O. Daramola et al. / Natural Science 3 (2011) 371-378 374
involved in anaerobic degradation of PTA wastewater
will definitely exhibit different roles at those conditions.
For mesophilic condition, a temperature range of 35˚C -
37˚C is necessary while for thermophilic degradation,
temperature of about 55˚C is essential [32]. In the case
study under consideration in this paper, the PTA waste-
water is generated at 54˚C - 60˚C, therefore, thermo-
philic treatment is preferable.
In addition, through the application of thermophilic
treatment, the use of cooling units required to cool the
PTA wastewater from 60˚C to 37˚C, which require addi-
tional costs, could be avoided. According to van Lier et al.
[33], thermophilic methanogenic consortia have, often, a
higher specific organic removal rate than the mesophilic
consortia. However, it is difficult, but important to get
the thermophilic organisms in the original inoculum and
to provide the required conditions for thermophilic deg-
radation [31]. Under mesophilic condition, δ-Proteoba-
cteria and the subcluster Ih of the group “Desulfoto-
maculum lineage I” [34] have been identified as the mi-
croorganisms responsible for the PTA wastewater deg-
radation under mesophilic condition. In addition, the
syntrophic methanogenic counterparts identified as Me-
thanosaeta concilii and members of Methanospirillum
and Methanobacteriaceae are the microorganisms which
play a role in the degradation process.
Some methods like Restriction Fragment Length Poly-
morphism (RFLP), Clone libraries and Fluorescence In-
Situ Hybridization (FISH) and Scanning Electron Mi-
croscopy (SEM) analysis are used to identify microbial
population and diversity in anaerobic degradation of
PTA wastewater during thermophilic condition. Accord-
ing to results from a SEM analysis, six different domi-
nant morphotypes have been identified to play signifi-
cant roles in degradation process of PTA wastewater
under thermophilic anaerobic degradation condition [31].
According to the authors, the dominant cells, the fat rods,
are responsible for TA degradation in the reactor. The
second most dominant cells, the bamboo-shaped cells,
and rods with flat ends (Methanosaeta-like species) are
methanogens that utilize acetate.
In clone library analysis, according to the investiga-
tion on phylotype. Methanothrix thermophila in the ace-
toclastic Methanosaeta group is found as the dominant
phylotypes. The remaining clones are related to mainly
hydrogen-utilizing Methanospirillum species [35]. The
Desulfotomaculum group is found to be the most domi-
nant that include diverse isolates and clone sequences
from various thermophilic and mesophilic environments
[36]. The desulfotomaculum group is also identified as a
dominant group according to the results of RFLP tech-
nique [31].
The FISH results with rRNA-targeted probes were
used to identify the domains Archaea (ARC915) and
Bacteria (EUB338_I/II/III). According to the results of
Loy et al. [37], the Desulfotomaculum group was identi-
fied as a dominant group with probe DFMI227a. Under a
microscopic examination, the authors observed that these
groups referred to the fat rods, are probably responsible
for TA degradation under thermophilic conditions. An-
other new probe TA55_OP5 was used to identify a dif-
ferent population. This probe hybridized to very small
rod shape cells, which have the second largest fraction in
the sludge. As a result of all methods used to analyze the
microbial community, the microbial diversity for ther-
mophilic degradation can be specified as Methanothrix
thermophila-related methanogens, Desulfotomaculum-
-related bacterial populations in the Gram-positive
low-G+C group and OP5-related populations, which are
responsible for degradation of terephthalate.
5. KINETICS OF PTA WASTEWATER
DEGRADATION AND REACTOR
DESIGN
Kinetics of the system is essential to determining the
volume and hydraulic retention time (HRT) of the reac-
tor in both mesophilic and thermophilic conditions. In
order to study the kinetics of degradation, in many cases,
some assumptions are made due to insufficient data from
literature. To justify and validate these assumptions, ex-
periments are carried out to obtain the kinetic parameters.
In the scenario presented in this paper, loading rate of
about 10 kg COD m−3·day−1 [26] for mesophilic condi-
tion and 16 kg COD m−3·day−1 [31] for thermophilic
condition were assumed for the reactor. For mesophilic
and thermophilic conditions, the solid (sludge) retention
time (SRT) was assumed to be 40 days based on the re-
ports presented in Reference [26] and Reference [31].
The authors also reported hydraulic retention time (HRT)
of 5 to 8 h in their studies. The operating conditions
adap- ted in the computation of HRT, the reactor volume
and the chemical oxygen demand (COD) content per m3
wastewater for the scenario presented in this study are
presented in Table 2. The HRT obtained was obtained
using Eq.1:
H
RTV Q

(1)
where HRT is the hydraulic retention time (h); V, the
bioreactor volume in m3 and Q, the flow rate in m3·h−1.
The computed HRT was between 15 and 24 h. This val-
ue is higher than HRT reported in Reference [26] and
Reference [31] despite using the same SRT. The dis-
crepancy can be attributed to the assumptions made in
this study. Furthermore, it has been understood that the
SRT could be high because of the low growth rate of the

M. O. Daramola et al. / Natural Science 3 (2011) 371-378 375
Table 2. Data used for bioreactor design.
Wastewater
characteristic
Thermophilic
condition
Mesophilic
condition
COD (kg COD m−3) 10.25 10.25
Maximum loading rate
(kg COD m−3·day−1) 16 10
Solid Retention Time
(SRT), day 40 40
PTA degrading bacteria. Therefore, based on the com-
puted SRT, volume of bioreactor required for the degra-
dation was calculated.
The value obtained for the COD was 10.4 kg COD m−3.
By considering different effluent flow rates from the
production plant, the total loading rate, in kg COD/day,
was computed. By dividing the flow rate with the maxi-
mal loading rate gives the minimum reactor volume re-
quired for the PTA wastewater degradation. For meso-
philic condition, the minimum reactor volume required
is ca. 1 m3 per 1 m3 wastewater flow per day and for
thermophilic condition, ca. 0.6 m3 reactor volume per 1
m3 wastewater flow per day is required. Although, the
reactor volume required for PTA wastewater degradation
depends on the wastewater flow rate from the production
plant. Having considered this, attempt was made to
compute reactor volume at different wastewater flow
rates for both mesophilic and thermophilic conditions.
Figure 3 depicts the reactor volume as a function of the
flow rate. From the reactor volume, the HRT was com-
puted using Eq.1. Minimum HRT of 24.6 h and 15.4 h
were obtained for mesophilic condition and thermophilic
condition, respectively:
As it can be seen in Figure 3, smaller reactor volume
is required for thermophilic anaerobic degradation com-
pared to mesophilic anaerobic degradation to treat the
same volume of PTA wastewater. This finding is cor-
roborated by the studies of Kleerbezem et al. [26] and
Chen et al. [31] where it has been shown experimentally
that the TA conversion rate is higher in the thermophilic
compared to mesophilic.
6. CONCLUSIONS AND FUTURE
OUTLOOK
Processes involved in the anaerobic treatment of TA
wastewater have been discussed from the perspective a
case study. A good choice to treat the PTA wastewater,
as presented in this case study, is through thermophilic
anaerobic degradation reactor. To degrade the amount of
the PTA wastewater, one-stage anaerobic reactor will be
required for thermophilic condition while at mesophilic
condition degradation two-stage reactor is required. How-
ever in both cases, and as suggested by Noyola et al.
Figure 3. Reactor volume as a function of flow rate.
[38], anaerobic degradation alone could not accomplish
effective PTA wastewater treatment because the sus-
pended solids in the raw wastewater could cause clog-
ging and accumulation of toxicity in the reactor [39].
Therefore, it is expected that post-treatment with an
aerobic unit could ensure the effluent quality below the
international waste disposal benchmark. However, a big
fluctuation in the removal efficiency of the reactor also
could pose a problem [31].
Thermophilic condition is preferable to mesophilic
condition, because with a one-stage reactor at thermo-
philic condition, the same removal rate can be achieved
as with a two-stage reactor at mesophilic condition. The
costs for a two-stage reactor are much higher than for a
one-stage process, so one-stage will be preferable. Also,
for the fact that the PTA wastewater stream exists at a
temperature of 54˚C - 60˚C, cooling units will be re-
quired to reduce the temperature before mesophilic deg-
radation is feasible. This eventually translates into addi-
tional cost for the treatment of the PTA wastewater. But
in thermophilic degradation, no cooling unit is required.
Moreover, in both cases, the pH of the wastewater
should be raised to 6 - 7 by adding alkali because the
microbial degrading kinetics is at optimum at this condi-
tion.
Regarding the future perspective of anaerobic biodeg-
radation of PTA wastewater, in-depth investigation of
anaerobic degradation mechanism and bio-kinetics is
essential. Although, Farjdo et al. [27] reported an inves-
tigation on anaerobic degradation mechanism and bio-
kinetics using upflow anaerobic sludge blanket (UASB)
reactor for easily biodegradable compounds, viz., acetic,
benzoic and formic acids from PTA wastewater, however,
more research efforts are still needed, especially, for PTA
wastewater treatment. As suggested by Karthik et al. [1],
pretreatment of PTA wastewater with coagulation-floc-
culation prior to biodegradation is techno-economically

M. O. Daramola et al. / Natural Science 3 (2011) 371-378 376
viable for the treatment of non-biodegradable PTA waste
water. Thus, more research efforts are required on the
optimization of this process when coupled with anaero-
bic treatment. Additionally, stable and effective reactors
are required.
In the 1970’s, Lettinga and his co-workers at Wagen-
ingen University in The Netherlands developed upflow
anaerobic sludge blanket (UASB) reactor for anaerobic
degradation of wastewater. A schematic of a typical
UASB reactor is presented in Figure 4. Some research
efforts also have been carried out with the use of biofilm
reactors with attached growth medium for microbes
[22,26,31]. Furthermore, in the laboratory, different ex-
perimental set-ups have been proposed and used for ex-
perimentations. Figure 5 depicts the down flow tubular
fixed film reactor proposed and used by Noyola et al.
[38] for PTA wastewater treatment. The experimental
set-up was made with plexiglass column of 1 m high and
96 mm internal diameter and packed with 21 polyvinyl
chloride (PVC) tubes of each, 670 mm high and 12.7 mm
diameter. In total, the reactor could provide 1.05 m2
support area and a void volume of 4.75 L. According to
Noyola et al. [38], compared to UASB reactors, down-
flow tubular fixed-film reactor has good resistance to
shock loads and periods without feeding, major limita-
tions in anaerobic treatment of PTA wastewater.
In the same vein, Pophali et al. [40] proposed and
used a laboratory scale upflow anaerobic fixed-film
fixed-bed reactor (AFFFBR) (see Figure 6) to investigate
PTA wastewater treatment. The reactor was made of glass
with reactor volume 2.43 L. Also, about 1.45 L of the total
volume of the reactor was occupied with 10 - 20 mm (size)
stones resulting in void volume 0.98.
Major problems in the anaerobic treatment of PTA
wastewater have been identified to be chemical inhibition
effects and shock loads [38]. To overcome these limita-
tions, expanded-bed granular activated carbon (GAC)
anaerobic reactors have been developed and implemented
to investigate the treatment of PTA-containing waste
water [41-44]. Figure 7 depicts a typical example of an
expanded-bed granular activated carbon (GAC) anaero-
bic reactor. Going by the studies of Tsuno and Kawamura
[41], the reactor can be made of a thick Plexiglas tube
with a diameter of 100 mm, occupying 10 L volume. 1.5 kg
GAC with a particle size of 0.9 - 1.1 mm is placed in the
reactor as the attached growth medium. The liquid in the
reactor can be circulated from the top part to the bottom to
expand the GAC medium by 25%, resulting in an ex-
panded-bed volume of 4.3 L. The concept behind the
mechanism of the reactor is based on the physical and
biological removal mechanisms. In the physical removal
mechanism, adsorption of inhibitory chemicals is by
adsorption onto GAC while the biological removal is
Figure 4. Upflow anaerobic sludge blanket (UASB) reactor.
Figure 5. Downflow tubular fixed-film reactor (Adapted from
Reference [38]).
Figure 6. Upflow anaerobic-aerobic fixed-film fixed-bed reactor
(UAFFFBR) (Adapted from Reference [40]).
through degradation by microorganisms growing on the
GAC. Through the adsorptive function of the GAC, effect
of the inhibitory chemicals and effect of shock loads are
minimized. Despite series of reactors that have been
proposed and developed, there is still need for further
research efforts toward optimizing and up-scaling of
these reactors for anaerobic treatment of PTA wastewater.
Therefore, it is expected that the scenario presented in
this paper will be thought provoking, especially, for
chemical/process engineers, environmental engineers,

M. O. Daramola et al. / Natural Science 3 (2011) 371-378 377
Figure 7. An expanded-bed granular activated carbon (GAC)
anaerobic reactors (Adapted from Reference [41]).
scientists and other professionals in environmental ma-
nagement, particularly in the area of industrial wastewa-
ter treatment. In addition, application of the process di-
agnosed in this paper is possible in the treatment of other
petrochemical wastewater such as, phenol-containing
wastewater, benzene/benzoic acid-containing wastewater
or wastewater from other similar industrial settings.
7. ACKNOWLEDGEMENTS
MOD is grateful to the authority of Obafemi Awolowo University,
Nigeria, for study leave to carry out this study.
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