Production Of Biopolymer By Bacillus Subtilis Isolated From Palm Oil Mill Effluent (Pome) And Its Application For Color Removal

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Date
2016-09
Authors
Khiew, Siee Kung
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Abstract
In this study, bacteria were isolated from Palm Oil Mill Effluent (POME) collected from anaerobic pond of MALPOM Industry, Penang. According to the sequencing results using Blast software of National Centre for Biotechnology Information, the bacteria isolated are B.subtilis, P.pabuli and E.cloacae. The optimum flocculation efficiency in treating kaolin clay suspension for: B.subtilis at 48 hours with 71.26 % flocculation efficiency; P.pabuli at 96 hours with 15.46 % flocculation efficiency; E.cloacae at 72 hours with 29.95 % flocculation efficiency. Therefore, B.subtilis is the only isolated bacteria that able to produce biopolymer for flocculation. Subsequently, B.subtilis was further analyzed for its optimal growth rate and biopolymer production. The optimum growth rate for B.subtilis is at 48 hours which is correlated to the highest amount of biopolymer yielded. Additionally, the flocculation efficiency showed the highest flocculation efficiency (71.26 %) at 48 hours. Hence, flocculation efficiency in treating suspended solid and dye wastewater by applying biopolymer produced by B.subtilis at 48 hours was determined. The biopolymer was able to treat 71.64 % of 5000 mg/L kaolin suspension at the optimal dosage of 42 mg/L whereas 98.64 % removal for reactive red 120 at the optimal dosage of 38 mg/L. The turbidity of the color solution decrease from 13.70 at 14 mg/L to 3.78 NTU at optimum dosage of biopolymer (38 mg/L). The mechanism involves are charge neutralization and sweep flocculation whereby the biopolymer neutralized the particles charges and agglomerate entire colloidal particles for settling. Besides that, the hybridization of biopolymer with cation in enhancing the flocculation efficiency was distinguished. Addition of metal ions to hybridize with biopolymer greatly affects the flocculation efficiency. Biopolymer hybridized with four different types of metal ions (K+, Ca2+, Mg2+, and Al3+) respectively are compared. The results show 44.34 % flocculation efficiency for K+, 70.10 % flocculation efficiency for Ca2+, 61.45 % flocculation efficiency for Mg2+, and 53.66 % flocculation efficiency for Al3+. This is because addition of metal ions to hybridize with biopolymer could help to increase the positive charge of the biopolymer surface. Lastly, the flocculation efficiency between calcium hybridized biopolymer (CaHP) and polyacrylamide was compared. Reactive red 120 color removal for CaHP is 98.64 % with 38 mg/L whereas PAM is 68.29 % with 30 mg/L after treated by alum. The novelty of this study is CaHP has the capability to further enhance the color removal compared to PAM which has no significant increment of color removal after coagulation by alum (62.59 %). CaHP has the capability to act as charge neutralizer since the cationic compound (Ca2+) bonded at the biopolymer can further agglomerate dye particles, resulted to higher color removal. In contrast to PAM, there is no further neutralization happened but agglomeration to form larger flocs size for settling. In overall, biopolymer produced by B.subtilis is able to treat suspended solid and dye wastewater through charge neutralization and sweep flocculation mechanisms. Additionally, biopolymer hybridized with metal ions can help to enhance the flocculation efficiency.
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B.subtilis is the only isolated bacteria that able , to produce biopolymer for flocculation.
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