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Nisola G.M.,Myongji University | Orata-Flor J.,Myongji University | Oh S.,Myongji University | Yoo N.,Ilshin Environmental Engineering Co. | Chung W.-J.,Myongji University
Desalination and Water Treatment | Year: 2013

Ammonia removal via nitrite was performed in membrane-aerated biofilm reactors (MABR). Two types of hollow fiber (HF) modules, uncoated microporous polyvinylidene fluoride (PVDF) and composite polyether-block-polyamide copolymer (PEBA) coated PVDF, were used as supports for the growth of ammonia oxidizing microorganism biofilm system. For the composite HF, a suitable coating material was selected between hydrophilic and hydrophobic types of PEBA. Results reveal that hydrophobic PEBA 2533 was more suitable for bacterial adhesion. The formation of coating layer was successfully confirmed through field emission scanning electron microscope. Other surface characterizations were performed through atomic force microscopy and contact angle measurements. Partial nitrification experiments at varied feed concentrations and hydraulic retention times reveal that MABR with uncoated PVDF HF exhibited slightly higher ammonia removal than the MABR with composite HF. In terms of nitrified products, MABR with composite HF produced > 90% of the removed ammonia in nitrite form. On the other hand, around 50% of nitrite was converted to nitrate in the MABR with uncoated PVDF. Thus, between the two membranes tested, PEBA 2533 coated PVDF is the more suitable HF for ammonia removal via nitrite formation in the MABR system. © 2013 Copyright Balaban Desalination Publications. Source


Nisola G.M.,Myongji University | Redillas M.C.F.R.,Myongji University | Cho E.,Korea Environment Institute | Han M.,Myongji University | And 2 more authors.
Biochemical Engineering Journal | Year: 2011

Three packing materials for sulfur oxidizing denitrification packed bed systems seeded with acclimated anoxic sludge were evaluated. Two porous media were prepared via thermal fusion with sodium bicarbonate as porogen: sulfur fused with powdered (1) calcium carbonate (CaCO3) (SCa) and (2) oyster shell (SCr). Randomly packed sulfur and limestone granules (S+L) media were used as the control. Results revealed that SCr is the most suitable media as it exhibited the highest nitrate removals and lowest nitrite accumulation. It has macrovoidal pores which facilitated microbial attachment. Additionally, SCr had the highest CaCO3 loading per unit volume and highest media dissolution rate which was favorable to avert pH decrease. But due to high denitrification activity, high sulfate levels in SCr may necessitate a post-treatment step prior to effluent discharge. Due to poor biomass attachment, S+L is most sensitive to change in fluid flow condition. As hydraulic retention time is decreased, S+L exhibited intensive and irreversible performance decline. Inferior denitrification performance of SCa was mainly due to low CaCO3 loading per unit volume, low dissolution kinetics and low alkalinity consumption by denitrifiers. Using modified Stover-Kincannon kinetic model, overall performance and denitrification capacities can be arranged as SCr>S+L>SCa. © 2011 Elsevier B.V. Source


Farnazo D.M.C.,Myongji University | Nisola G.M.,Myongji University | Han M.,Myongji University | Yoo N.,Ilshin Environmental Engineering Co. | Chung W.-J.,Myongji University
Bioprocess and Biosystems Engineering | Year: 2012

Biodegradations of methyl ethyl ketone and methyl isobutyl ketone were performed in intermittent biotrickling filter beds (ITBF) operated at two different trickling periods: 12 h/day (ITBF-12) and 30 min/day (ITBF-0.5). Ralstonia sp. MG1 was able to degrade both ketones as evidenced by growth kinetic experiments. Results show that trickling period is an important parameter to achieve high removal performance and to maintain the robustness of Ralstonia sp. MG1. Overall, ITBF-12 outperformed ITBF-0.5 regardless of the target compound. ITBF-12 had high performance recovery at various inlet gas concentrations. The higher carbon dioxide production rates in ITBF-12 suggest higher microbial activity than in ITBF-0.5. Additionally, lower concentrations of absorbed volatile organic compound (VOC) in trickling solutions of ITBF-12 systems also indicate VOC removal through biodegradation. Pressure drop levels in ITBF-12 were relatively higher than in ITBF-0.5 systems, which can be attributed to the decrease in packed bed porosity as Ralstonia sp. MG1 grew well in ITBF-12. Nonetheless, the obtained pressure drop levels did not have any adverse effect on the performance of ITBF-12. Biokinetic constants were also obtained which indicated that ITBF-12 performed better than ITBF-0.5 and other conventional biotrickling filter systems. © Springer-Verlag 2011. Source


Jeon B.-H.,Yonsei University | Choi J.-A.,Yonsei University | Kim H.-C.,Yonsei University | Kim H.-C.,Ilshin Environmental Engineering Co. | And 5 more authors.
Biotechnology for Biofuels | Year: 2013

Background: Microalgal biomass contains a high level of carbohydrates which can be biochemically converted to biofuels using state-of-the-art strategies that are almost always needed to employ a robust pretreatment on the biomass for enhanced energy production. In this study, we used an ultrasonic pretreatment to convert microalgal biomass (Scenedesmus obliquus YSW15) into feasible feedstock for microbial fermentation to produce ethanol and hydrogen. The effect of sonication condition was quantitatively evaluated with emphases on the characterization of carbohydrate components in microalgal suspension and on subsequent production of fermentative bioenergy. Method. Scenedesmus obliquus YSW15 was isolated from the effluent of a municipal wastewater treatment plant. The sonication durations of 0, 10, 15, and 60 min were examined under different temperatures at a fixed frequency and acoustic power resulted in morphologically different states of microalgal biomass lysis. Fermentation was performed to evaluate the bioenergy production from the non-sonicated and sonicated algal biomasses after pretreatment stage under both mesophilic (35°C) and thermophilic (55°C) conditions. Results: A 15 min sonication treatment significantly increased the concentration of dissolved carbohydrates (0.12 g g-1), which resulted in an increase of hydrogen/ethanol production through microbial fermentation. The bioconvertibility of microalgal biomass sonicated for 15 min or longer was comparable to starch as a control, indicating a high feasibility of using microalgae for fermentative bioenergy production. Increasing the sonication duration resulted in increases in both algal surface hydrophilicity and electrostatic repulsion among algal debris dispersed in aqueous solution. Scanning electron microscope images supported that ruptured algal cell allowed fermentative bacteria to access the inner space of the cell, evidencing an enhanced bioaccessibility. Sonication for 15 min was the best for fermentative bioenergy (hydrogen/ethanol) production from microalga, and the productivity was relatively higher for thermophilic (55°C) than mesophilic (35°C) condition. Conclusion: These results demonstrate that more bioavailable carbohydrate components are produced through the ultrasonic degradation of microalgal biomass, and thus the process can provide a high quality source for fermentative bioenergy production. © 2013 Jeon et al.; licensee BioMed Central Ltd. Source

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