Int. J. Environ. Res. Public Health 2008, 5(3) 177-180
International Journal of
Environmental Research and Public Health
© 2008 by MDPI
© 2008 MDPI. All rights reserved.
Electrocoagulation of Palm Oil Mill Effluent
Melissa B. Agustin1,2, Waya P. Sengpracha3* and Weerachai Phutdhawong4*
1Dept. of Chemistry, Faculty of Science, Maejo University, Sansai, Chiang Mai 50290, Thailand
2Dept. of Chemistry, College of Arts and Sciences, Central Luzon State University, Science City of Muñoz, Nueva Ecija, 3120,
3Dept. of Chemistry, Faculty of Science, Silpakorn University, Nakhon Pathom 73000, Thailand
4Dept. of Science, Faculty of Liberal Arts and Science, Kasetsart University, Kamphaeng Saen, Nakorn Pathom 73140, Thailand.
*Correspondence to Dr. Weerachai Phutdhawong and Dr. Waya P. Sengpracha. E-mail: firstname.lastname@example.org or
email@example.com and firstname.lastname@example.org
Received: 20 February 2008 / Accepted: 21 March 2008 / Published: 30 September 2008
Abstract: Electrocoagulation (EC) is an electrochemical technique which has been employed in the treatment of various
kinds of wastewater. In this work the potential use of EC for the treatment of palm oil mill effluent (POME) was
investigated. In a laboratory scale, POME from a factory site in Chumporn Province (Thailand) was subjected to EC
using aluminum as electrodes and sodium chloride as supporting electrolyte. Results show that EC can reduce the
turbidity, acidity, COD, and BOD of the POME as well as some of its heavy metal contents. Phenolic compounds are also
removed from the effluent. Recovery techniques were employed in the coagulated fraction and the recovered compounds
was analysed for antioxidant activity by DPPH method. The isolate was found to have a moderate antioxidant activity.
From this investigation, it can be concluded that EC is an efficient method for the treatment of POME.
Keywords: POME treatment; Electrocoagulation, Phenolic compound
Palm oil mill effluent (POME) is an important source
of inland water pollution when released without treatment
into local rivers or lakes. POME has generally been
treated by anaerobic digestion, resulting in methane as a
value-added product [1,2]. Many methods have been
reported in the literature regarding the treatment of POME
such as treatment using a pond system  and aerobic
digestion of POME to decrease carbon content and
inorganic nitrogen with consequent change of pH from the
acidic range to an alkaline one . Other treatments
include one that increases the ratio of organic nitrogen,
leading to the production of a better fertilizer , a
pretreatment using Moringa oleifera seeds as an
environmentally friendly coagulant , a treatment in an
up-flow anaerobic sludge fixed film bioreactor , an up-
flow anaerobic sludge fixed film bioreactor using response
surface methodology (RSM) , methane emission from
anaerobic ponds , semi-commercial closed anaerobic
digester  and by synthetic polyelectrolytes . As far
as we know, electrocoagulation (EC) has not yet been
reported as a treatment for palm oil mill effluent. In this
study, EC, a distinctly
environmentally-friendly choice for meeting wastewater
discharge standards is reported as an alternative method
for POME treatment. Moreover, in this investigation, the
coagulum was recovered and the antioxidant activity of
the isolate was determined.
Materials and Methods
The palm oil mill effluent used in this study was
collected at Chumporn Palm Industries, Chumporn,
Electrocoagulation of POME and Isolation of Potential
Prior to EC, residual oil in POME was rid of by
extracting with hexane in a separatory funnel. One litre of
the de-oiled POME was then transferred to a glass
economical and an
Int. J. Environ. Res. Public Health 2008, 5(3)
cylindrical vessel (inner diameter: 12 cm, height: 23 cm)
with a special cover to support a pair of aluminium
electrodes having a dimension of 30cm x 10cm x 1mm.
Sodium chloride (2.0g) was added to the solution as
supporting electrolyte. The electrodes were immersed 4
cm apart and 8 cm deep into the solution which was kept
stirred throughout the experiment. Crotech (Model
ZT3202) was used to supply the solution with a direct
current (1.4-2.0 A, 3.50-12V). Electrocoagulation was
continued for a total of 6 hrs excluding the time consumed
for replacing the electrodes every hour. After the
electrolytic process, the solution was filtered using
vacuum filtration. The clear filtrate (370 ml) obtained__the
effluent after EC__ was kept in a glass bottle and stored in
the refrigerator for analysis and the coagulum was
collected and dried in an oven at 40oC. The dried
coagulum was pulverised and dissolved with 7% HCl in
the ratio of 1 g coagulum: 5ml acid. The acid-coagulum
mixture was kept stirred to ensure complete dissolution
and was then transferred to a separatory funnel. An equal
volume of 1-butanol (n-BuOH) was added and the mixture
was shaken vigorously and allowed to separate overnight.
The n-BuOH extract was collected and the remaining
aqueous solution was further extracted with n-BuOH
twice. All the n-BuOH extracts were combined and
washed with water three times to remove any trace of
inorganic compounds from the aqueous layer. The n-
BuOH was removed using vacuum rota-evaporation which
enabled the recovery of the solvent. The residual
compounds (presumably containing mainly the phenolic
compounds from POME) were further dried at 40o C in an
COD and BOD5 Determination
COD and BOD5 of the palm oil mill effluent before
and after EC were determined according to the Standard
Methods for Examination of Water and Wastewater .
COD was analyzed using the closed reflux titrimetric
method. Briefly, the method involves refluxing a known
volume of sample with an oxidizing agent (K2Cr2O7/H-
2SO4) in a closed ampule at 150 °C for two hours, and
titrating the excess oxidizing agent with standard ferrous
ammonium sulfate using ferroin as indicator. BOD5
determination involves filling
overflowing, a BOD bottle of the specified size and
incubating it at 20oC for 5 days. Dissolved oxygen (DO) is
measured initially and after incubation using titrimetric
method and the BOD is computed from the difference
between the initial and final DO. All determinations were
done in duplicate.
The concentrations of the following metals: Cu, Cr,
Mn, Fe and Pb in the POME before and after EC were
analyzed in the filtered samples using Flame-Atomic
Absorption Spectrophotometry (Perkin Elmer Analyst
100). The detection limit was estimated as the standard
with sample, to
deviation of the concentrations of blank samples
multiplied by three.
DPPH Free Radical Scavenging Assay of the POME
Solutions of the POME isolate containing mainly the
recovered phenolic compounds were prepared at varying
concentrations (1000, 500, 250, 100, 50 ppm) in methanol.
0.20 μM 1,1-Diphenyl-2-picrylhydrazyl
methanolic solution (3 mL) were added to the POME
isolate solution (1 mL). For blank analysis, MeOH (1 mL)
was used. The decrease in concentration of DPPH as a
measure of antioxidant activity was measured via UV-Vis
spectrophotometer (ThermoSpectronic) at 517 nm. The
antioxidant activity was compared with a standard solution
of Vitamin E.
Results and Discussion
Electrocoagulation of POME and Isolation of Possible
Table 1 shows the comparison of POME before and
after EC. Electrocoagulation of the POME afforded a clear
solution from a dark brown, opaque effluent (Figure 1).
Table 1: Comparison of POME solutions before and after
Color Dark brown
Before EC After EC
Turbidity Opaque Transparent (clear)
pH 4.30 7.63
FeCl3 test Positive Negative
COD 36,800 ± 283 mgL-1
25,600 ± 354mgL-1
23,400 ± 848 mgL-1 14,400 ± 1272 mgL-1
The pH of the solution also increased from 4.30 to
7.63 after EC. This could be explained by the formation of
aluminium hydroxyl ions according to the following
Anode reaction: Al → Al3+ + 3e-
Cathode reaction: 2H2O + 2e- → 2OH- + H2
Overall reaction: 2Al + 6H2O → 2Al(OH)3 + 3H2
The aluminium can either react directly to an organic
compound that contains negatively charged atoms, or form
polymeric Al+3 hydroxo complexes, eg. aluminium
hydroxide [Al(OH)3], that can remove pollutants by
adsorption to produce charge neutralization and by
enmeshment in a precipitate or coagulum .
Int. J. Environ. Res. Public Health 2008, 5(3)
Figure 1: POME before (A) and after (B) electro-
Before EC, the presence of phenolic groups in the
POME was confirmed by the formation of a black-blue
solution after the FeCl3 test. After EC, the reaction of the
POME solution with the FeCl3 test gave a negative result
(clear solution). With this simple test, it was demonstrated
that the phenolic substances present in the effluent were
virtually removed after EC, presumably mainly by
complexation with aluminium ion and subsequent
The partial removal of dissolved organic substances
from POME was also confirmed by the decrease in
chemical oxygen demand (COD) and biochemical oxygen
demand in a 5-d test period (BOD5) after EC. The mean
values for COD and BOD5 before and after EC were
significantly different at 95% confidence level. The mean
COD level in POME before EC was 36,800 mgL-1 which
was reduced to 25,600 mgL-1, corresponding to a 30%
removal. BOD5 reduced from 23,400 mgL-1 to 14,400
mgL-1 (38% removal). The observed percentages of
removal for COD and BOD5 from this study were lower
than that determined by the study of Ugurlu et al.  in
the electrocoagulation of paper mill effluent which
registered 75 and 70% removal of COD and BOD,
respectively. However, it has to be noted that in that study
the initial COD and BOD levels of the paper mill effluent
were approximately 86 and 900 times lower, respectively,
than the initial COD and BOD of POME. It is also
interesting to note that the averaged COD and BOD of
POME before and after EC were significantly different at
95% confidence level. The removal of COD and BOD by
electrocoagulation could be attributed to the removal of
suspended solids and to precipitation of dissolved organic
molecules as organometallic compounds . Dissolution
of the coagulum from a liter of POME followed by
extraction afforded 17.1 grams of a black, flaky isolate
that was tested for its antioxidant activity.
Presented in Table 2 is the change in the
concentration of some representative common heavy
metals analyzed in POME before and after EC. From this
result, it is evident that EC can remove not only the
organic constituents in the effluent, but also the inorganic
contents like heavy metals, in agreement with many
previous findings relating to EC .
Table 2: Metal content of POME before and after EC
Metals Before EC (ppm) After EC (ppm)
0.036 0.059 ± 0.01
40.57 ± 0.06
0.008 ± 0.001-
nd – not detected
DPPH Antioxidant Test
As reported in the prior discussion, some organic
compounds including phenolic substances were removed
during EC. With the assumption that these phenolic
substances were successfully recovered from the
coagulum through the isolation techniques employed in
this study and in light of the known fact that phenolic
compounds are good antioxidants, the POME isolate was
tested for its antioxidant activity. The antioxidant activity
of the POME isolate was determined by its ability to
reduce the activity of the stable free radical
diphenylpicrylhydrazyl (DPPH) and was compared with
Vitamin E, a known antioxidant. It can be seen from
Figure 2 that the absorbance of the DPPH radical solution
decreased with increasing concentration of the POME
isolate. However, the decrease in absorbance for the
POME isolate did not match that of the Vitamin E. From
the absorbance values, the percentage reduction was
calculated using the equation:
Ab - As
10.44 ± 0.02
where Ab is the absorbance of the blank solution and
As is the absorbance of the sample.
0 50100 250 5001000
Figure 2: Absorbance values of the DPPH radical solution
against the concentration of antioxidant.
x 100% reduction =
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Shown in Figure 3 is the plot of the percentage
reduction in DPPH radical at various concentrations of
antioxidant. The POME isolate gave only 60.34 %
reduction at 1000 ppm concentration, while Vitamin E
gave 94.68% at the same concentration. Calculation of the
equation of the line for each curve enabled the
determination of the EC50, the effective concentration of
the antioxidant at which 50% of the activity of the DPPH
radical has been reduced. For Vitamin E, the EC50 was
determined to be 106 ppm while that of the POME isolate
was 723ppm. The antioxidant activity of the POME isolate
could possibly be increased by further purification.
0 50100 250500 1000
Figure 3: The percentage reduction in the activity of
DPPH radical against the concentration of antioxidant.
It can be concluded from this study that EC can be a
useful method for the treatment of palm oil mill effluent.
EC enabled the removal of suspended solids, dissolved
organic substances and some heavy metals in, and reduced
the acidity, COD and BOD of the effluent. However, to
obtain a higher percentage removal for COD and BOD,
further study on optimization of the method is encouraged.
The isolated organic compounds after recovering from the
coagulum exhibited antioxidant activity which is lower
than that of Vitamin E. The possibility of using the isolate
as antioxidant for natural rubber could be of interest for
Acknowledgements: The authors gratefully acknowledge
the financial support from Thailand Research Fund
(RDG4850071 and MRG495S054). Dr. T. Cheunbarn's
research group from Maejo University was acknowledged
for COD and BOD facilities.
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