April 2014, Volume 5, No.2 International Journal of Chemical and Environmental Engineering
Wheat Germ as Natural Coagulant for Treatment of Palm Oil Mill Effluent (POME) Nor Shazwani Daud; Tinia Idaty Mohd Ghazi*; Intan Salwani Ahamad Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia UPM Serdang, Selangor, Malaysia * Corresponding Author E-mail:
[email protected]
Abstract: The potential of wheat germ as a natural coagulant for treatment of palm oil mill effluent (POME) was explored. A series of jar test was conducted for the determination of best extraction method for the wheat germ, optimum dosage and optimum pH. The reported parameters were turbidity, TSS, COD and colour. It was found that the wheat germ extracted with 1M NaCl solution (WG-1M) achieved the highest reduction of turbidity, TSS, COD and colour at 99.1%, 95.6%, 61.7% and 67.8% respectively. This was attained at optimum dosage of 12 000 mg/L and an optimum pH of 2. Results showed that the wheat germ can be regarded as a new potential natural coagulant for the treatment of POME. Keywords: Wheat germ; natural coagulant; extraction method; palm oil mill effluent (POME); jar test.
1. Introduction Palm oil industry in Malaysia started in the year 1920 with 400 hectares of oil palm cultivated. More cultivation areas were opened up as direct consequences of crop diversification policy by government. In 2013, more than 18 million tons of palm oil was exported [1]. Result from the growth of the palm oil industry, the milling and refining sectors also increased. Besides the empty fruit bunches, mesocarp fibers and shell, palm oil mill effluent (POME) is one of the wastes produced from the processing of oil palm fresh fruit bunches (FFB) in the production of palm oil [2]. From every tonne of fresh fruit bunches being processed, it is estimated that 0.5-0.75 tons of POME discharged. POME cannot be discharged directly to the land, as it will adversely affect the soil and vegetation system. It is also cannot be discharged into the watercourses directly without treatment as the good quality of water bodies for aquatic lives will be depleted and distracted. Since 1980’s ponding system is the most conventional and applicable method, used in treating POME in Malaysia. Though the system is cheap in cost and easy to operate, but it requires large area with long retention time and difficult to maintain biogas collection, which produces bad odor and liquor distribution [3]. The application of coagulation-flocculation process using natural coagulant was found to be a new alternative for POME treatment [4]. Chemical coagulant such as Alum (aluminium sulphate) is commonly used as coagulant in the coagulation process for water and wastewater treatment.
However the existence of Aluminum could lead to health problems as aluminum has correlation to Alzheimer’s disease [5]. From the findings, sporadic studies have been carried out to replace the function of chemical coagulants by using natural coagulants originate from natural plants (moringa oleifera, nirmali seeds, cactus, tannin, dragon fruit) and animal (chitosan obtained in inverterbrates) [68]. Moringa oleifera (MO) is the most studied coagulant compared to other plant based coagulants as its history in water purification was explored at the beginning of 20 th century [9]. Protein was found to be the active component in the seeds of MO [10] and this cationic protein reacts through charge neutralization by-being attached to the negatively charged particles in wastewater for formation of floc in coagulation. The extraction of active component from MO can be improved by using salt solution as an extractant rather than using distilled water. At the same initial turbidity of 50 NTU of synthetic wastewater, MO extract with salt solution (MOC-SC) gave percentage turbidity reduction to be more than 95% at 4 mL/L dosage, where the dosage used was 7.4 times lower than MO extract with ordinary distilled water (MOC-DW) with 32mL/L dosage at only 78% turbidity reduction [11]. Meanwhile the use of dragon fruit foliage as natural coagulant in the treatment of concentrated latex effluent could lead to removal of turbidity, SS and COD at 99.7%, 88.9% and 94.7% respectively [8]. At pH 6, chitosan was able to reduce the turbidity, TSS and COD levels of POME by 99.9%, 99.2% and 60.7% respectively [12]. As discussed by previous researchers, active coagulating component from the plants extracts was the protein [13].
Wheat Germ as Natural Coagulant for Treatment of Palm Oil Mill Effluent (POME)
Wheat germ is a by-product of the flour milling process. Compared to other wheat product (such as wheat bran and wheat flour), the wheat germ contain the highest value of protein which constitutes about 27%, followed by wheat bran (14%), wheat flour (13%) and only small portion for other wheat products [14]. The availability of protein in the wheat germ (WG) is the factor it is chosen as potential of natural coagulant in this research project. The aim of this research is to investigate the effectiveness of wheat germ (WG) as a potential bio coagulant for the treatment of POME.
2. Materials and Method Materials Wheat germ seeds were purchased locally from Pesimon Cereal Resources Sdn Bhd. The WG seeds were ground to fine powder using a laboratory mill. The ground seeds were sieved through 0.4 mm sieve and 30 g of the prepared powder was suspended in 1 L of different solvents such as the distilled water (WG-DW), tap water (WG-TW) and 0.25, 0.5 and 1M NaCl labeled as WG0.25M, WG-0.5M and WG-1M solution, respectively. The coagulation active component was extracted through the stirring of the suspension using magnetic stirrer for 10 minutes and filtered through 47 mm filter paper. This filtered solution is called as extracts. The extract was stored at 4oC temperature until use. Raw POME sample was obtained from palm oil mill located at Dengkil, Selangor at a temperature range from 80-900C before cooled to room temperature for experimental work. Characteristics of raw POME are presented in Table I. Raw POME is thick brownish liquid which slightly acidic and contains large amounts of solids, high value of biochemical oxygen demand (BOD) and chemical oxygen demand (COD). It was collected directly into a thermal resistant plastic container, which was then labeled and tightly sealed before being transported into the laboratory. It is then kept at the cold room at 4 0C to avoid biodegradation process from microbial activity.
at temperature in the range of 25-30oC. Each of the six beakers was filled with 250 mL of POME. The suspension was then added with different coagulant dosage range from 7000 mg/L to 15 000 mg/L and stirred at 120 rpm for 1 minute as rapid mixing. The speed was reduced to 35 rpm for 25 minutes as slow mixing. The suspension was left for 1 hour to settle and the supernatant was then withdrawn using a pipette for turbidity, TSS, COD and colour measurement. The pH was adjusted within the range of 2-12, by using 1M NaOH or 1M HCl. Analytical Method The turbidity and pH was measured using Hach turbidimeter model 2100N and pH meter (HACH USA) respectively. The COD was performed through the closed reflux method using the APHA standard methods of examination of water and wastewater. With the aid of vacuum filtration apparatus, the suspended solid (SS) was determined through gravimetric method while the total solid was determined through the determination of material left after the sample had been evaporated and undergoes subsequent drying in an oven at 103oC to 105oC. The colour was recorded using HACH spectrophotometer Model DR 2500.
3. Result and Discussion Effect of Solvents and Dosage on WG Performance Effect of different solvents in extracting the WG at different dosage on the coagulation performance was analyzed. WG acts as primary coagulant at original pH of POME sample, i.e. 5. From Fig. 1, treatment of POME with WG-1M achieved the highest removal of turbidity, which is 97.7% at optimal dosage of 12 000 mg/L. The dosage was the optimum for WG-1M as no significant improvement in turbidity removal with further coagulant addition. WG-0.5M recorded a turbidity reduction at 96.5%, and WG-0.25M at 96.4%.
Table 1. Initial Characteristics of Raw POME Parameters pH
Raw POME 4.78
Turbidity
25 730 NTU
Total suspended solid (TSS)
18 400 mg/L
Total solid (TS)
38 000 mg/L
Chemical Oxygen Demand (COD)
48 000 mg/L
Colour
17 500 Pt Co
Jar Test Phipps and Bird stirrer jar test apparatus, which comprises of six-spindle steel paddles together with six beakers were used in this experiment. This experiment was conducted
Figure 1. Effect of different solvents in extracting WG and dosage on turbidity removal and POME residual turbidity.
Meanwhile, the WG-DW and WG-TW recorded 94.2% and 92.9% respectively. The residual turbidity recorded at this dosage was 580 NTU, 897 NTU, 923 NTU, 1505 NTU and 1825 NTU for WG-1M, WG-0.5M, WG-
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Wheat Germ as Natural Coagulant for Treatment of Palm Oil Mill Effluent (POME)
0.25M, WG-DW and WG-TW respectively. Fig. 2 shows the TSS reduction at 93.5%, 92.8%, 89.1%, 87% and 85.8% after the addition of WG-1M, WG-0.5M, WG-0.25M, WG-DW and WG-TW respectively to POME suspension. The residual TSS was recorded to be 1194 mg/L, 1326 mg/L, 2005 mg/L, 2393 mg/L and 2609 mg/L respectively. COD reduction was the highest for WG-1M, which is 55% followed by 52% for WG-0.5M and 51.7% for WG-0.25M. In addition to that, 48% and 43.3% of the COD reduction was recorded for WG-DW and WG-TW respectively. This is shown in Fig. 3. The residual COD recorded was 21 600 mg/L, 23040 mg/L, 23200 mg/L, 24960 mg/L and 27200 mg/L for WG-1M, WG-0.5M, WG-0.25M, WG-DW and WG-TW respectively.
6503 Pt Co, 7457 Pt Co and 7516 Pt Co for WG-1M, WG-0.5M, WG-0.25M, WG-DW and WG-TW respectively.
Figure 4. Effect of different solvents in extracting WG and dosage on colour reduction and POME residual colour.
Figure 2. Effect of different solvents in extracting WG and dosage on TSS reduction and POME residual TSS.
The efficiency in coagulation performance is increased with the application of salt as an extraction method for the WG and the higher the concentration of NaCl, the better the coagulation performance. This result is similar to the result obtained by Okuda et al. [10], where the dosage of moringa oleifera extracted with 1M NaCl solution was 32 mL/L which is 7.4 times lower as compared to those extracted with distilled water (4 mL/L). With salt solution, moringa oleifera coagulate more than 95% of 50 NTU initial kaolin turbidity, while moringa oleifera extracted with distilled water could only coagulate 78% at the same initial kaolin turbidity. The result was also similarly obtained by the work done by Sarpong et al. [15], where the use of salt solution as solvent in extracting the active component from moringa oleifera lead to higher turbidity removal (94%), compared with those without salt solution (54%) at the same coagulant dosage. This phenomenon could be explained due to existence of protein in the WG [14] as protein is said by many researchers to be an important element in promoting coagulation [9]. The solubility of protein in water due to formation of hydrogen bond between amino acids and water molecules as shown in Fig. 5.
COD reduction and POME residual COD.
As can be seen in Fig. 4, the application of WG-1M into POME suspension obtained the highest color reduction of 65.2%. This was followed by WG-0.5M with 64.3% and WG-0.25M with 62.8%. Meanwhile, WG-DW and WG-TW recorded percentage of colour reduction at 57.4% and 57.1% respectively. The residual colour recorded was 6086 Pt Co, 6255 Pt Co,
Figure 5. Formation of hydrogen bond between amino acids and water molecules [16]
At the same time, there is also attractive force between individual protein molecules through formation of hydrogen bond. Such forces could lead to aggregation of protein and less solubility in water molecules. This
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Wheat Germ as Natural Coagulant for Treatment of Palm Oil Mill Effluent (POME)
interaction can be seen in Fig. 6. As salt add to the solution, the solubility of protein in water increases [10]. Since NaCl used in this research is a strong electrolyte, which completely dissociate into Na+ and Cl- ion in water, this additional ion will shield ionic charge at protein’s surface and decreases the attractive forces which prevent aggregation between protein molecules and protein solubility in water could be promoted.
Figure 8. Effect of POME pH on all parameters
Figure 6. Hydrogen bond between protein molecules [16]
The higher level of protein soluble in the coagulation solution (due to salt influence) resulted in better coagulation performance. Since the operating pH of POME is in acidic condition (i.e. 5), the amino groups in the protein were being protonated. Fig. 7 shows the protonation of amino acid in the acidic condition. Since particles in POME is negatively in charge [6], the protonated amino acid in wheat germ is attracted to negatively charged particles, and this will promotes coagulation as these particles bind to each other and growth in size to form a floc. As a result, larger particle or floc become heavy and settle to the bottom.
Figure 7. Protonation of amino acid in acidic condition [16]
Good coagulation performance was traced at pH 2,3,4, and 5; of these, pH 2 is the optimum. The reduction of turbidity, TSS, COD, and colour at pH 2 were recorded to be 99.1%, 95.6%, 61.7% and 67.8%, respectively. Meanwhile, pH 11 shows the lowest coagulation performance with only 54.9%, 33.7%, 26.7% and 43% reduction of turbidity, TSS, COD and colour respectively. This result is similar to the work carried out by Abu Hassan et al. [6], where the optimum pH was at acidic pH solution, i.e. 6 with the removal of turbidity, TSS and COD reported to be 99.9%, 99.15% and 60.73%, respectively for the treatment of POME using chitosan. Other work done by Bhatia et al. [17], also obtained the optimum pH at acidic condition i.e. 5 with the removal in suspended solids and the COD reduction was 95% and 52.2%, respectively by using moringa oleifera. This may be due to the positive charges of amino acid in the acidic solution while, negative at basic solution. These negatively charged amino acids repel the negatively charged particles in the wastewater such as POME and thus, coagulation process become poorer at basic condition. The structure of amino acid in basic solution is represented in Fig. 9.
Effect of POME pH on WG performance The optimum pH of the treatment system was obtained through the study of the effect of pH on WG-1M performance. This study is important as the surface charge of the coagulants and stabilization of the suspension is affected by the pH of POME suspension. The pH of POME was adjusted from pH 2 to pH 12. WG1M was used as the best extraction method with an optimal dosage of 12 000mg/L, underwent 120 rpm rapid mixing, 35 rpm slow mixing, 25 minutes mixing time and 1 hour settling time. Fig. 8 shows the same trend for all parameter reduction, which is higher at acidic and lower in alkaline conditions.
Figure 9. Structure of amino acid in basic solution [16]
4. Conclusion Wheat germ extracted with 1M NaCl solution (WG-1M) recorded the highest removal of turbidity, TSS, COD and colour with optimum dosage of 12 000 mg/L and at optimum pH of 2. The removal of turbidity, TSS, COD and colour at this optimum condition were 99.1%, 95.6%, 61.7% and 67.8%, respectively. This significant finding would be a potential new development in POME treatment with natural and biodegradable coagulant. It is recommended that wheat germ be applied to other types of wastewater treatment in the future work.
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Wheat Germ as Natural Coagulant for Treatment of Palm Oil Mill Effluent (POME)
ACKNOWLEDGMENT The authors would like to acknowledge the Department of Chemical and Environmental Engineering, Universiti Putra Malaysia for providing facilities and technical support, and Seri Ulu Langat Palm Oil Mill Sdn. Bhd. for providing the POME samples.
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