IMIeJ2012-Organic Pollutants Removal From Diluted Palm Oil Mill Effluent (POME)

8/11/2019 IMIeJ2012-Organic Pollutants Removal From Diluted Palm Oil Mill Effluent (POME)

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Organic Pollutants Removal From Diluted Palm Oil Mill Effluent (POME)Through Sono Fenton nZVI Process.

M. R. Taha1,a

, A. H. Ibrahim2,b,*

, A. W. Azhari2,c

M. A. Wahab2,d

1Department of Civil and Structure Engineering, Universiti Kebangsaan Malaysia, 26000, Malaysia

2School of Environmental Engineering, Universiti Malaysia Perlis, 01000, Malaysia

[email protected], [email protected], [email protected],[email protected]

Keywords: palm oil mill effluent (POME), sono-Fenton, zero valent iron

Abstract. In this study, an advance Fenton process called sono-Fenton-nZVI process was used to

remove organics content from palm oil mill effluent (POME). Factors such as pH, sonication

intensity and sonication time were studied in order to see their effects on organic removal

efficiency. Sono-Fenton-nZVI process very much dependent on the presence of ferrous ion (Fe

2+

).At pH 2, nZVI particles oxidized rapidly to produce sufficient Fe2+which is very crucial in Fenton

process. Through sono-Fenton-nZVI process, 80% of the organic content was removed after 24

hour of silent degradation. However, at higher sonication intensity and longer sonication period theprocess was accelerated. Same removal efficiency was achieved after 2 hours instead of 24 hours of

silent degradation. Hence, the application of sono-Fenton-nZVI process seems to be a promising

treatment method to remove the organic pollutants from POME.

INTRODUCTION

Palm oil production is one of the major industries in Malaysia and ranked as worlds second largest

exporter of palm oil after Indonesia. In the year 2010, Malaysia had produced approximately 17.2million tonnes of crude palm oil (CPO) which were produced from 416 palm oil mills located

throughout the country [1]. All mills operated in the country currently employed wet milling

process which directly used large amount of water. In return, large volumes of waste water were

also produced which usually called as palm oil mill effluent (POME).

Data shows that raw POME contain average of 25,000 mg/l biochemical oxygen demand (BOD)

and 55,250 mg/l of chemical oxygen demand (COD) [2]. While during the high-crop season, the

values of BOD and COD in POME can rise up to 49,000 mg/L and 79,000 mg/L respectively [3].

Study by [2,3] indicates that POME is extremely rich in organic loads and directly poses very high

risk to environmental pollution if it not well treated before being emitted into the water bodies. Due

to extremely high content of organic loadings, several stages of treatment process have been appliedby the mill operators in order to meet the discharge limit impose by the local authority. Currently,

certain mill operators treat their POME up to tertiary/ polishing treatment to ensure the effluent

comply the discharge limit.

In most cases, aerobic process (activated sludge or membrane filters) is employed in

tertiary/polishing treatment plant. An evaluation study on tertiary treatment plant in palm oil mills

by Wahab [4] indicates that COD removal through the treatment process can only removed an

average of 56% of initial COD content. While Johari [5] reported that palm oil mills which

employed activated sludge process for the tertiary treatment also shows similar removal efficiency.

Since the microorganisms are very sensitive to the environmental changes, a very intensive care

should be carried out to ensure the survival of the microorganisms.


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Besides using biological approaches, applications of advance oxidation processes (AOPs)

particularly Fenton process to remove COD from different types of wastewater such as olive mill

effluent [6], industrial wastewater [7] and landfill leachate [8, 9] also widely studied. During Fenton

process, hydroxyl radical (OH)produced from the reaction of Fe2+and hydrogen peroxide (H2O2)

attack and degrade the organic compounds hence reduce the COD content in the wastewater.

In Fenton process, the removal efficiency of organic compounds is very much dependent on pH,

dosage of H2O2 and Fe2+ [10]. Besides hydroxyl radical (OH) that is beingproduced, Fe

2+ also

being oxidized to ferric ion (Fe3+). The reactions occur during the Fenton process are as below:

Fe2++ H2O2 Fe3++ OH+ OH

(1)

Fe3++ H2O2 Fe2++ OOH+ H

+ (2)

In addition, reaction in Eq. 2 is slower compared to reaction in Eq. 1 where at certain point, the

ferrous ion concentration will be decrease and the production of OH will become less [11].

Consequently removal efficiency of organic compounds from the wastewater will be affected.

To overcome the drawbacks, exposure to ultrasound irradiation is one of the solutions.

Ultrasound irradiation can accelerate Eq. 2 where the level of Fe2+ concentration can be keep at

adequate level to maintain the fenton process. In addition, OH can also be produced through the

cavitation of water molecules during the sonolysis process hence reduce the volume of H2O2used in

Fenton process [12]. The reactions can be represent as:

H2O +))) OH + H (3)2OH + 2H H2O2 + H2 (4)

In conventional Fenton process, iron sulfate (FeSO4) is used as major source of Fe2+ [13].

Application of nZVI particles in Fenton process as an alternative to iron salt has been proven to

reduce the cost of Fenton process. Nano size ZVI particles will provide more reactive surface area

hence contribute to the success of Fenton process. In addition, the recycling rate of Fe3+ also

become faster when nZVI particles are used in the Fenton process. The reaction can be represent

through the following reaction [14]:

2 Fe3+ + Fe 3Fe2+ (5)

The objective of this study is to investigate the effects of pH, sonication intensity and sonication

time in Fenton process while utilizing nZVI particles as Fe

2+

source on COD removal of dilutedpalm oil mill effluent (POME).

MATERIALS AND METHODS

Chemicals. Hydrogen peroxide (R&M Chemicals, 30%), Sulfuric acid (Merck, 95-97%), Sodium

Hydroxide (Merck, M=40g/mol), nZVI particles (Nanofer Star by NANO IRON, s.r.o., 80%) withaverage particle size to 50 nm.

Experimental procedures. Concentrated raw palm oil mill effluent (POME) was diluted 25 times

with distilled water. The average initial CO concentrations of the diluted samples were 1160 mg/L


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respectively. pH of the diluted samples were then adjusted to pH 2 and pH 4 using sulfuric acid

(0.5M).

100 ml of sample was then placed in a water-jacketed cylindrical glass reactor. For every 100 ml

sample, 0.06 g of nano zero valent iron and 0.4 ml of hydrogen peroxide was added. The mixture

was then subjected to sonocation using an ultrasonic probe (Sonic Ruptor 250, 20kHz, OMNIInternational).

Immediately after the sonication process, 15 ml of samples were taken out and centrifuged at

4000 rpm for 10 minutes and tested for COD content via closed refluxed method. Remaining

samples then were placed in an automatic shaker for silent degradation of COD. COD analysis was

also done after 1 hour, 2 hours and 24 hours of silent degradation.

The experimental design was generated using full factorial design in statistical software called

Design Expert version 7.1 by Stat- Ease Company. The levels and independent variables for the

experimental design are shown in Table 1. Each run was replicated 3 times and average COD

removal was recorded for analysis.

Table 1: Levels and independent variables for the experimental design

Run Sonication intensity

(%)

Sonication time

(min)

pH

1 20 5 2

2 40 5 2

3 20 15 2

4 40 15 2

5 20 5 4

6 40 5 4

7 20 15 4

8 40 15 4

RESULT AND DISCUSSION

Oxidation Of Nano Zero Valent Iron Particles (Nzvi). Nanofer Star are very reactive nZVI

particles, which in the presence of water, will be oxidized into Fe2+. With high specific surface area

and ultrasound assisted, the productions of Fe2+ from nZVI particle occurred rapidly. High

concentration of Fe2+ will improve the Fenton process through the conversion of H2O2 to OH by

Fe2+ [15]. Fig. 1 shows the production of Fe2+ from nZVI particle at different process condition.

Result shows that at pH 2, nZVI particles were oxidized most compared to pH 4. At pH 4, the

production of Fe

2+

was very low. This was in agreement with a study by Kellel and Namkung [14,16] where Fe2+produced from iron by corrosion was increased with the decreasing value of pH.


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Fig 1: The Fe2+concentration at different silent degradation time and process condition.

At pH 2, combination on high sonocation intensity and longer sonocation time help to boost the

production of Fe2+in the samples. This condition can be seen through run 4 where almost 700 mg/L

of Fe2+ were produced immediately after sonication process. Concentration of Fe2+ will reduce

gradually due to the reaction of H2O2 to produce OH as mentioned in Eq. 1. However, after 2 hours

of silent degradation, the concentration of Fe2+ starts to increase back. At this stage, Fe3+produced

from Eq. 1 started to react with H2O2 to reproduce Fe2+through Eq. 2.

The Effect of pH, Sonication Power And Sonication Time On COD Removal. Immediately after

the sonication process, COD readings in all samples were increased except for run 4. Results based

on the treatment processes is represented in Fig. 2. This phenomenon occurred due to the presence

of remaining H2O2 in the samples which interfered the COD analysis [17]. During the COD

analysis, besides the organic pollutants, the remaining H2O2 was also oxidized by the oxidizing

agent, hence increased the COD reading. It obviously happened in all samples treated at pH 4. AtpH 4, there were very minimal Fe2+present to react with H2O2to produce hydroxyl radical (OH).

Due to that, more H2O2 available in the samples and contribute larger interference to the COD

analysis. The effect of H2O2 concentration on COD reading is represented in Figure 3. As can been

seen in Figure 3, addition of 0.4 ml of hydrogen peroxide into 100 ml of distilled water will rise up

the COD reading up to 1332 mg/L.

Fig 2: COD removal from diluted POME Fig 3: Effetc of H2O2 on COD readings.

samples

As for samples treated at pH 2, it clearly shows that COD removal in all samples were increased

by time. It can be explain by the presence of Fe2+ in these samples due to the oxidation of nZVI


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which later react with H2O2to OH. Longer silent degradation produced more hydroxyl radical OH

and help to remove COD from POME samples. After 24 hours of silent degradation, 68 - 80% of

COD content was removed through sono-Fenton-nZVI process.

On the other hand, COD reading in samples which were treated at pH 4 went back to their initial

COD content after 24 hours of silent degradation. These indicate no COD removal from the dilutedPOME samples. In these samples, all added H2O2 were decomposed into water and oxygen. The

decomposition of H2O2 can be represent in the following equation:

2 H2O2 2 H2O+ O2 (6)

Sonication intensity or sonication time gave no significant effect on COD removal efficiency of

diluted POME. Figure 2 shows that samples which were treated at pH 4 at various sonication

intensity and sonication time resulted in almost the same COD removal. Similar trends were also

noticed in treatment condition 1, 2, and 3. COD removal efficiency for these three treatment

conditions was not much different. This result matched the finding by R. Chand [18]. Through his

study, samples were treated at two different high ultrasound frequency (300 and 520 kHz). Eventhough the samples were treated at two different frequencies, the total organic removal were almost

the same for both samples. However, combination of high power and longer sonication time

boosted the COD removal efficiency. This clearly happened in treatment process 4. At this

treatment condition, the maximum COD removal (80%) can be achieved in 2 hours instead of 24

hours of silent degradation.

CONCLUSION

Application of NZVI particles can be an alternative to the usage of iron sulfate in conventional

Fenton process. In sono-Fenton-nZVI process, pH of the sample plays a major role to the success of

the process. At pH 2, nano zero valent iron particles will produce sufficient Fe2+to react with H2O2and reduce the organic content from the POME sample through the sono-Fenton-nZVI process. In

addition, an exposure to high sonication intensity and longer sonication time will accelerate the

COD removal process. Hence, the application of sono-Fenton-nZVI process seems to be a

promising treatment method to remove organic content from POME.

REFERENCES

[1] S. Sidik, Regulatory requirement on POME discharge and compliance, Paperwork NationalSeminar on Biogas and Palm Oil Mill Effluent Treatment (Biogas POMET), Unpublished

result.[2] Y. S. Wong, M. O. Kadir, T. T. Teng, Biological kinetics evaluation of anaerobic stabilizationpond treatment of palm oil mill effluent, Bioresour Technol 100 (2009) 49694975.

[3] E. P. Phaik, J. Y. Wei, F. C. Mei, Palm oil mill effluent (POME) characteristic in high cropseason and the applicability of high-rate anaerobic bioreactors for the treatment of POME, Ind

Eng Chem Res 49 (2010) 1173211740.[4] N. A. Wahab, Status of DOE MPOB survey on POME at palm oil mills , Paperwork

National Seminar on Biogas and Palm Oil Mill Effluent Treatment (Biogas POMET),Unpublished result.

[5] Z. Johari, The Development of POME treatment technologyFELDA experience, PaperworkNational Seminar on Biogas and Palm Oil Mill Effluent Treatment (Biogas POMET).

Unpublished result


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[6] S. L. Marco, A. P. Jose, Removal of COD from olive mill wastewater by Fenton's reagent:kinetic study, J Hazard Mater 168 (2009) 12531259.

[7] B. Barbara, D. M. Ida, V. Francesco, Fenton treatment of complex industrial wastewater:Optimization of process condition by surface response method, J Hazard Mater 186 (2011)

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[8] Z. Hui, J. C. Heung, P. H Chin, Multivariate approach to the Fenton process for the treatmentof landfill leachate, J Hazard Mater B136 (2006) 618-623

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11381142.[13] M. S. Lucas, J. A. Peres, Removal of COD from olive mill wastewater by Fentons reagent:

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[15] X. Zhu, J. Tian, R. Liu and L. Chen, Optimization of Fenton and electro-Fenton oxidation ofbiologically treated cooking wastewater using response surface methodology. Sep Purif

Technol 81 (2011) 444450.[16] K.C. Namkung, A.E. Burgess, D. H. Bremmer, H. Staines, Advanced Fenton processing of

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IMIeJ2012-Organic Pollutants Removal From Diluted Palm Oil Mill Effluent (POME)

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