Thrumakunasagran, Vjayan (2018) Effect Of Famine-Phase Aeration On Polyhydroxyalkanoate Accumulation In Aerobic Granules. Masters thesis, Universiti Sains Malaysia.
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Abstract
Polihidroksialkanoat (PHA) adalah polimer biodegradasi yang telah menarik minat dalam kalangan para penyelidik akhir-akhir ini. PHA boleh dihasilkan dengan menggunakan butiran aerobik yang merawat air sisa. Walau bagaimanapun, kos pengeluaran yang tinggi, terutamanya disebabkan oleh penggunaan pengudaraan yang tinggi, telah mengehadkan aplikasi biopolimer ini. Dalam kajian ini, kesan pengudaraan yang berubah-ubah dalam fasa substrat terhad ke atas keupayaan penumpukan PHA dan morfologi butiran aerobik telah disiasat. Empat reaktor penjujukan berkelompok telah diinokulasi dengan butiran aerobik dan dikendalikan pada kadar pengudaraan yang berbeza menggunakan air sisa kilang minyak sawit sebagai substrat tunggal. Kadar pengudaraan berterusan sebanyak 2.0 L/min digunakan dalam fasa substrat berlebihan (FSB) dan fasa substrat terhad (FST) untuk Reaktor 1 (kawalan). Sementara itu, kadar pengudaraan semasa FSB dalam Reaktor 2, 3 dan 4 adalah sama dengan Reaktor 1 manakala kadar pengudaraan semasa FST dikurangkan kepada 1.0 L/min, 0.5 L/min dan 0 L/min masing-masing dalam Reaktor 2, 3 dan 4. Keputusan Reaktor 1 menunjukkan bahawa lebih daripada 90% suapan COD berjaya disingkirkan secara purata dan kandungan PHA maksimum sebanyak 56% berat kering sel telah ternumpuk di dalam butiran aerobik. PHA yang terkumpul adalah kopolimer poli (3-hidroksibutirat-co-3-hidroksivalerat) (P3 (HB-co-HV)) dengan kandungan hidroksivalerat (HV) 21%. Butiran aerobik mempunyai saiz butiran purata, indeks isipadu enapcemar dan kandungan substrat polimerik sel (EPS) masing-masing sebanyak 1030 μm, 41 mL / g dan 829.50 μg / g biojisim. Sementara itu, kajian pengudaraan yang berubah-ubah mendedahkan bahawa semua butiran aerobik mencapai penyingkiran COD dan kandungan PHA yang sama, tanpa mengira kadar pengudaraan yang digunakan dalam FST. Terutamanya, apabila kadar pengudaraan yang rendah digunakan semasa FST, masa yang diambil untuk mencapai kandungan PHA maksimum telah menjadi singkat dengan ketara. Tambahan pula, perubahan komposisi PHA berlaku, di mana kandungan HV telah meningkat. Tambahan lagi, pengurangan kadar pengudaraan telah meningkatkan jumlah kandungan EPS dalam butiran aerobik, secara tidak langsung meningkatkan keupayaan pengenapan butiran. Pengurangan kadar pengudaraan dari 2.0 L/min ke 0.5 L/min telah mengakibatkan peningkatan saiz butiran dengan peratusan jumlah tertinggi. Sebaliknya, ketebalan lapisan mikroorganisma penumpukan PHA pada permukaan butiran didapati telah menurun apabila kadar pengudaraan dalam FST dikurangkan. Secara keseluruhan, hasil kajian menunjukkan bahawa keperluan pengudaraan dalam FST untuk penumpukan PHA dalam butiran aerobik adalah kurang penting. Penghasilan PHA dalam butiran aerobik di bawah pengudaraan sifar dalam FST boleh mengakibatkan pengurangan tenaga sehingga 74%, yang pada dasarnya dapat mengurangkan kos pengeluaran keseluruhan biopolimer ini. _______________________________________________________________________________________________________ Polyhydroxyalkanoate (PHA) is a biodegradable polymer which has attracted a lot of interests among researchers lately. PHA can be feasibly produced using aerobic granules treating wastewater. However, high production costs, particularly due to the high aeration used, have limited the applications of this biopolymer. In this study, the effect of variable aeration rates in the famine period on the PHA accumulating capability and morphology of aerobic granules was investigated. Four sequencing batch reactors were inoculated with aerobic granules and operated at different aeration rates using palm oil mill effluent as the sole substrate. A feast-famine constant aeration rate of 2.0 L/min was used for Reactor 1 (control). Meantime, the feast period aeration rate of Reactor 2, 3 and 4 was similar to that of Reactor 1 while the famine period aeration rate was decreased to 1.0 L/min, 0.5 L/min and 0 L/min in Reactor 2, 3 and 4, respectively. The findings of Reactor 1 show that more than 90% of the influent chemical oxygen demand (COD) was removed on average and a maximum PHA content of 56% cell dry weight was accumulated in the aerobic granules. The PHA accumulated was a copolymer of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (P3(HB-co-HV)) with 21 % hydroxyvalerate (HV) content. The aerobic granules had an average granular size, sludge volume index and extracellular polymeric substance (EPS) content of 1030 μm, 41 mL/g and 829.50 μg/g biomass, respectively. Meanwhile, the variable aeration study reveals that regardless of the aeration rates used in the famine period, all aerobic granules achieved a similar COD removal and PHA content. Notably, under a famine period with low aeration rate, the time taken to reach the maximum PHA content had decreased significantly. Moreover, PHA compositional changes occurred, where the HV content had increased. Further, the decrease in the famine period aeration rate enhanced the total EPS content of the aerobic granules, indirectly improving the settling ability of the granules. The reduction in aeration rate from 2.0 L/min to 0.5 L/min has resulted in an increased size of granules with the highest volume percentage. On the other hand, the thickness of the layers of PHA accumulating microorganisms at the surface of the granules was found to have decreased when the famine period aeration rate was reduced. Overall, the results indicate that the requirement of aeration for PHA accumulation in aerobic granules is highly insignificant in the famine period. PHA production in aerobic granules under zero aeration in the famine period may result in an energy input reduction of up to 74%, which could essentially reduce the overall production cost of this biopolymer.
| Item Type: | Thesis (Masters) |
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| Uncontrolled Keywords: | Full text is available at http://irplus.eng.usm.my:8080/ir_plus/institutionalPublicationPublicView.action?institutionalItemId=4618 |
| Subjects: | T Technology T Technology > TP Chemical Technology > TP200-248 Chemicals: Manufacture, use, etc. |
| Divisions: | Kampus Kejuruteraan (Engineering Campus) > Pusat Pengajian Kejuruteraan Kimia (School of Chemical Engineering) > Thesis |
| Depositing User: | Mr Mohd Jasnizam Mohd Salleh |
| Date Deposited: | 06 May 2019 07:41 |
| Last Modified: | 06 May 2019 07:41 |
| URI: | http://eprints.usm.my/id/eprint/44291 |
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