Chang-Min Ahn

Comparative enzyme inhibitive methanol production by Methylosinus sporium from simulated biogas.

Methane in a simulated biogas converting to methanol under aerobic condition was comparatively assessed by inhibiting the activity of methanol dehydrogenase (MDH) of Methylosinus sporium using phosphate, NaCl, NH4Cl or EDTA in their varying concentrations. The highest amount of methane was indistinguishably diverted at the typical conditions regardless of the types of inhibitors: 35°C and pH 7 under a 0.4% (v/v) of biogas, specifically for <40 mM phosphate, 50 mM NaCl, 40 mM NH4Cl or 150 µM EDTA. The highest level of methanol was obtained for the addition of 40 mM phosphate, 100 mM NaCl, 40 mM NH4Cl or 50 µM EDTA. In other words, 0.71, 0.60, 0.66 and 0.66 mmol methanol was correspondingly generated by the oxidation of 1.3, 0.67, 0.74 and 1.3 mmol methane. It gave a methanol conversion rate of 54.7%, 89.9%, 89.6% and 47.8%, respectively. Among them, the maximum rate of methanol production was observed at 6.25 µmol/mg h for 100 mM NaCl. Regardless of types or concentrations of inhibitors differently used, methanol production could be nonetheless identically maximized when the MDH activity was limitedly hampered by up to 35%.

The removal of 1,4-dioxane from polyester manufacturing process wastewater using an up-flow Biological Aerated Filter (UBAF) packed with tire chips

1,4-Dioxane is one of the by-products from the polyester manufacturing process, which has been carelessly discharged into water bodies and is a weak human carcinogen. In this study, a laboratory-scale, up-flow biological aerated filter (UBAF), packed with tire chips, was investigated for the treatment of 1,4-dioxane. The UBAF was fed with effluent, containing an average of 31 mg/L of 1,4-dioxane, discharged from an anaerobic treatment unit at H Co. in the Gumi Industrial Complex, South Korea. In the batch, a maximum of 99.5 % 1,4-dioxane was removed from an influent containing 25.6 mg/L. In the continuous mode, the optimal empty bed contact time (EBCT) and air to liquid flow rate (A:L) were 8.5 hours and 30:1, respectively. It was also found that the removal efficiency of 1,4-dioxane increased with increasing loading rate within the range 0.04 to 0.31 kg 1,4-dioxane/m3·day. However, as the COD:1,4-dioxane ratio was increased within the range 3 to 46 (mg/L COD)/(mg/L 1,4-dioxane), the removal efficiency unexpectedly decreased.

Study on Characteristics of Solubilization for Sewage Sludge Using Electronic Field and Ultrasonification

Sludge solubilization using sonification has been increasingly used for sludge volume reduction along with enhancing digestion efficiency during anaerobic biogas production. In this study, either electric field or ultrasonification or in combination with were investigated using three types of sludge (return, excess and mixed at G sewage treatment facility) for the most efficient solubilization. As a the closed loop, 200 L of sludge was continuously passing through the solubilization system at an average flow rate of 0.7 m/h, which is equivalent to 3.5 times treated per hour for up to 84 times (24 h). Only implying electric field showed no variation for sCOD/tCOD before and after treatment on sludge solubilization regardless of types of sludge. However, employing the ultrasonic or combined system could both increasingly solubilize sludge with regard to the number of passing-through, which more enhanced by the combined. In addition, VSS/TSS was lowered to in the range of 2 and 6% while its particle size, diameter (0.9) and diameter (0.5) were more minimized than that of raw sludge. For return sludge, ultrasonification was more efficiently facilitated for solubilization, whereas electric field-ultrasonification was more preferably applied for excess and mixed sludge. It is concluded that depending on types of sludge, solubilization system must be selectively applied for the most efficient break-up of them.

Monitoring of Geothermal Systems Wells and Surrounding Area using Molecular Biological Methods for Microbial Species

This study was conducted to monitor microbial species dynamics within the aquifer due to long term operation of geothermal heat pump system. The species were identified by molecular biological methods of 16S rDNA. Groundwater sample was collected from both open (S region) and closed geothermal recovery system (J region) along with the control. J measured and control as well as S measured found Ralstonia pickettii as dominant species at year 2010. In contrast, Rhodoferax ferrireducens was dominantly observed for the control of S. In 2011, Sediminibacterium sp. was universely identified as the dominant species regardless of the monitoring places and type of sample, i.e., measured or control. The difference in the dynamics between the measured and the control was not critically observed, but annual variation was more strikingly found. It reveals that possible environmental changes (e.g. ORP and DO) due to the operation of geothermal heat recovery system in aquifer could be more exceedingly preceded to differentiate annual variation of microbial species rather than positional differences.

Characteristics of Methanol Production Derived from Methane Oxidation by Inhibiting Methanol Dehydrogenase

This study was conducted to biologically convert methane into methanol. Methane contained in biogas was bio-catalytically oxidized by methane monooxygenase (MMO) of methanotrophs, while methanol conversion was observed by inhibiting methanol dehydrogenase (MDH) using MDH activity inhibitors such as phosphate, NaCl, , and EDTA. The degree of methane oxidation by methanotrophs was the most highly accomplished as 0.56 mmol for the condition at and pH 7 under 0.4 (v/v%) of biogas ( 50%, 50%) / Air ratio. By the inhibition of 40 mM of phosphate, 50 mM of NaCl, 40 mM of and of EDTA, methane oxidation rate could achieve more than 80% regardless of type of inhibitors. In the meantime, addition of 40 mM of phosphate, 100 mM of NaCl, 40 mM of and of EDTA each led to generating the highest amount of methanol, i.e, 0.71, 0.60, 0.66, and 0.66 mmol when 1.3, 0.67, 0.74, and 1.3 mmol of methane was each concurrently consumed. At that time, methanol conversion rate was 54.7, 89.9, 89.6, and 47.8% respectively, and maximum methanol production rate was . From this, it was decided that the methanol production could be maximized as 89.9% when MDH activity was specifically inhibited into the typical level of 35% for the inhibitor of concern.

Enhancement of Dewaterability of Sewage Sludge by Ultrasonification and Electric Field Treatment

The sludge disposal is a major economic factor in the sewage treatment facility operation. Moreover, since the ocean dumping will be prohibited by Korean environmental law from 2013, sludge should be eliminated or sludge volumetric reduction should be performed urgently. In this study, improvement of the sewage sludge dewaterability was investigated by ultrasound and electric field treatment. Sludge was treated by a single or in combination of either the electric field or ultrasound on a pilot pretreatment facility, then it was dewatered by lab-scale filter press. The operating input energy of ultrasound device was varied from 225~1,200 kJ/L and electric field device was varied from 4.5~24 kJ/L. The water contents of dewatered sludge cake treated with ultrasound (1,200 kJ/L) and combination of ultrasound/electric field (1,224 kJ/L) were decreased 10~12% by comparing non-treated sludge. At that time, water contents were 65~66%. The combination treatment of ultrasound/electric field was effective to reduce water content of dewatered sludge cake, however, water content was not changed by a single treatment of electric field because of low energy density.

Comparative Assessment of Quantitative Methods determining the Amount of Calcium Carbonate Minerals derived from Biocalcification

This study was performed to develop a method for quantitative analysis obtaining the amount of calcium carbonate minerals formed when Ca salts biomimetically reacted with carbon dioxide. There were two methods compared; 1) volumetric calcimeter method that determining the amount of released carbon dioxide after calcium carbonate minerals were acidified by 4N HCl and 2) Thermogravimetry-Differential Thermal Analysis (TG-DTA) adopting differential decomposition temperature breaking-up the structural link within calcium carbonate minerals. The comparisons were made by batch experiment (i.e., biocalcification process) along with control (i.e., nominal concentration of prepared). For the control, TG-DTA took a minor root mean square deviation (RMSD) of 1.1~5.9 mg, whereas volumetric calcimeter exposed a greater RMSD of 28.3 mg. For the biocalcification, the amount of was more precisely obtained for TG-DTA rather than that of volumetric calcimeter. It was decided that TG-DTA was more successfully used for quantitative analysis to observe the amount of calcium carbonate minerals derived from biocalcification.

Characterization of CO 2 Biomineralization Microorganisms and Its Mineralization Capability in Solidified Sludge Cover Soil in Landfill

This study was performed to determine whether biomineralization microbes were actively present underneath landfill cover soil producing biocalcification. From this, various types of microbes were observed. Among them, two species were dominantly found; Bacillus megaterium and Alkaliphilus metalliredigens that were known as biominerlization bacteria. With those microbes, CO2 was more highly consumed than without bacteria. In response, the calcium carbonate mineral was produced at 30% (wt) greater than that of the control. At the same time, TG-DTA was successfully used for quantification of CO2 consumed forming calcium carbonate minerals resulting from biocalcification. It was decided that the presence of solidified sewage sludge cake utilized as a cover soil in the landfill could efficiently contribute to possible media adaptably and naturally sequestering CO2 producing from the landfill.

Assessment for

This study was conducted to characterize CO2 biomineralization on several minerals (i.e., CaO, MgO, SiO2) by bottle test in an aqueous solution and solidified sludge using different aerobic bacterial strains like Bacillus megaterium and Bacillus pasteurii by batch test. These bacteria promote the formation of microenvironments that facilitate the precipitation of mineral phases that were unsaturated in the bulk solution. For one type of mineral solely amended, the CO2 was reduced at the highest of 4.0 mmol for MgO while it was not that much lower for CaO and SiO2 showing 1.1 and 0.3 mmol CO2, respectively. For two types of minerals simultaneously amended, the CO2 was reduced at the greater extent for both Ca + Mg and Mg + Si showing 2.7 and 2.3 mmol, respectively whereas it was less for Ca + Si at 1.8 mmol. For solidified sludge, the CO2 reduction rate changed depending on the volume of solidified sludge placed in the medium and the input CO2 concentration.. The reduction rate of CO2 was increased with increasing the volume of solidified sludge. Results of XRD analysis indicate that CaCO3 (Calcite) was dominantly formed among others (e.g., Aragonite, Dolomite). SEM analysis showed that the sample with Bacillus pasteurii, could more form minerals rather than control. As demonstrated in this study, CO2 would be effectively sequestered in biomineralization process.