Young-Gyun Choi

A comprehensive overview on electro-active biofilms, role of exo-electrogens and their microbial niches in microbial fuel cells (MFCs)

Microbial fuel cells (MFCs) are biocatalyzed systems which can drive electrical energy by directly converting chemical energy using microbial biocatalyst and are considered as one of the important propitious technologies for sustainable energy production. Much research on MFCs experiments is under way with great potential to become an alternative to produce clean energy from renewable waste. MFCs have been one of the most promising technologies for generating clean energy industry in the future. This article summarizes the important findings in electro-active biofilm formation and the role of exo-electrogens in electron transfer in MFCs. This study provides and brings special attention on the effects of various operating and biological parameters on the biofilm formation in MFCs. In addition, it also highlights the significance of different molecular techniques used in the microbial community analysis of electro-active biofilm. It reviews the challenges as well as the emerging opportunities required to develop MFCs at commercial level, electro-active biofilms and to understand potential application of microbiological niches are also depicted. Thus, this review is believed to widen the efforts towards the development of electro-active biofilm and will provide the research directions to overcome energy and environmental challenges.

Enhancing biological treatment of dye wastewater with zero-valent iron

Pretreatment of authentic industrial dye wastewater with zero-valent iron (ZVI) was evaluated using a bench-scale integrated anaerobic-aerobic (ZVI-AO) biological treatment system. Average ADMI (American Dye Manufacturers’ Institute) value of dye wastewater was reduced from 245 to 107 units with ZVI column pretreatment. Subsequent treatment of ZVI column effluent by a continuous AO process further reduced the ADMI values to 18-39, resulting in overall decolorization efficiency of 78-89%. A control AO system without ZVI pretreatment, which was operated in parallel, achieved just 44-69% of ADMI removal efficiency. In addition, the ZVI integrated system yielded effluents with much lower COD and BOD concentrations than the control system. The aerobic batch respiration tests confirmed that ZVI treatment transformed the recalcitrant dye compounds to slowly biodegradable fractions, thus enhancing the overall biodegradability of dye wastewater.

Inorganic fouling control in reverse osmosis wastewater reclamation by purging carbon dioxide

Inorganic fouling on the membrane surface is one of the major prevalent issues affecting the performance and cost of reverse osmosis system. Chemical dosage is a widely adopted method for the inhibition of inorganic scale on the membrane surface. In this study, CO2 was used to control inorganic scale formation on surface of reverse osmosis (RO) membrane in wastewater reclamation. The pH of influent could be lowered by purging CO2. It caused an increase in solubility of inorganic salts in water resulting in discharge of principle ions in concentrate stream. A pilot plant study was conducted with four different RO modules including control, with dosage of antiscalant, with purging CO2 and with co-addition of antiscalant and CO2. The effectiveness of CO2 purging was assessed on the basis of operational analysis, in-line analysis and morphological results. Ryznar stability index was used to determine the scaling potential of system. The examined data indicated that CO2 purging was successful to inhibit scale formation on the membrane surface. Moreover, CO2 was found more eco-friendly than antiscalant, as no by-products were generated in concentrate stream.

Adsorptive removal of arsenate using inorganic magnetite particles

AbstractArsenic (As)-contaminated drinking water is a serious health problem in many parts of the world. Although magnetite particles have been shown to be effective at removal of arsenic from water, there has been no research to assess the feasibility of using mill scale-derived magnetite for water treatment. This project was conducted to evaluate magnetite particles as a cost-effective and eco-friendly As adsorbent. Mill scale iron waste has been used to prepare magnetite. The synthesized magnetite was fully characterized and used for the removal of arsenate anion from water. Magnetite showed adsorption capacity of 8.612xa0mg/g for arsenate anion. Desorption studies were done on the adsorbent to check the recyclability. Magnetite was regenerated with no change in arsenic removal efficiency.

Calibration of an ultraviolet distribution model by precise measurement of underwater ultraviolet intensities

In Korea, disinfection of effluent from a wastewater treatment plant is now essential, and ultraviolet (UV) disinfection is known as one of the useful disinfection alternatives. The non-contact type UV disinfection method, which is distinguished by a fouling-free process, was developed, and a mathematical model for the photoreactor was developed. For the purpose of the model calibration, the study had manufactured a non-contact type UV photoreactor and measured UV intensities within the photoreactor. The two major parameters of the model were evaluated by comparing the UV intensity of the photoreactor and the model’s simulation results. As the result of this study, the developed model for a non-contact type UV photoreactor could predict UV intensity within the photoreactor well. Optima parameter values came out as measuring 576 points for the calibration test and 504 points for the verification test. The coincidence index proved useful in calibrating the parameters, with the index values over 0.9 at the optimum values. This study produced optimum values for the two parameters. The UV conversion efficiency and the transmittance of UV in pure water came out to be 0.56 and 100%, respectively.

Mill Scale–Derived Magnetite Particles: Effective Adsorbent for the Removal of Phosphate in Aqueous Solutions

AbstractMill scale, an iron waste, was used to synthesize magnetite particles for the adsorption of phosphate from an aqueous solution. Several techniques were used to characterize the adsorbents. ...

Arsenate removal using a hybrid system of adsorbents and a microfiltration membrane

AbstractArsenate in drinking water is a serious concern to millions of people around the world. Although various technologies have been developed in recent years, one of the most sustainable technologies for removing arsenate from water in developing countries is the use of absorption in the treatment of drinking water. This study determined the surface characteristics and arsenic removal efficiency of a new adsorbent Fe–Mn–Si (FM-α) and compared the performance of a hybrid system using FM-α and a microfiltration membrane with a hybrid system using a traditional adsorbent (zero-valent iron, ZVI) and a microfiltration membrane. Surface area analyses employing electron microscopy and energy-dispersive X-ray spectroscopy obtained a specific surface area of FM-α (17.2xa0m2/g) that is 14 times that of ZVI (1.2xa0m2/g). The arsenate removal efficiency of FM-α was 51 and 14% at pH 4 and 7, respectively, in the presence of phosphate, and 89 and 94% at pH 4 and 7, respectively, in the presence of humic acid; all these...