Ji-Sun Han

Optimization of biological wastewater treatment conditions for 1,4-dioxane decomposition in polyester manufacturing processes.

The solvent stabilizer 1,4-dioxane could have harmful effects on an ecosystem. The discharge limit of 1,4-dioxane in a body of water will be regulated at 5 mg/L in Republic of Korea. Thus, the currently operating activated sludge used in the manufacture of polyester should be properly treated to meet the regulations. Accordingly, the removal rate of 1,4-dioxane and its microbial properties was assessed at K, H and T corporations. The highest removal efficiencies were recorded at H. However, the concentration of 1,4-dioxane in the effluent of T exceeded the criterion. In addition, a microbial degradation test was conducted on 100 mg/L of 1,4-dioxane inoculated with the activated sludge from each of the three corporations. After 7 days, the 1,4-dioxane was completely removed with the H sludge and efficiencies were 67% in the T sludge and 52% in the K sludge. These results confirm that the biodegradability of 1,4-dioxane may vary in relation to the microbial properties. The microbial diversity of activated sludge of each company was therefore investigated by 16S rDNA cloning methods. In conclusion, the activated sludge of H is the most effective for the biodegradation of 1,4-dioxane. This fact is of significant concern for the industrial sector.

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%.

Decomposition of 1,4-dioxane by photo-Fenton oxidation coupled with activated sludge in a polyester manufacturing process

The cyclic ether 1,4-dioxane is a synthetic industrial chemical that is used as a solvent in producing paints and lacquers. The EPA and the International Agency for Research on Cancer(IARC) classified 1,4-dioxane as a GROUP B2(probable human) carcinogen. 1,4-dioxane is also produced as a by-product during the manufacture of polyester. In this research, a polyester manufacturing company (i.e. K Co.) in Gumi, Korea was investigated regarding the release of high concentrations of 1,4-dioxane (about 600 mg/L) and whether treatment prior to release should occur to meet with the level of the regulation standard (e.g., 5 mg/L in 2010). A 10 ton/day pilot-scale treatment system using photo-Fenton oxidation was able to remove approximately 90% of 1,4-dioxane under the conditions that concentrations of 2800 ppm H(2)O(2) and 1,400 ppm FeSO(4) were maintained along with 10 UV-C lamps (240 microW/cm(2)) installed and operated continuously during aeration. However, the effluent concentration of 1,4-dioxane was still high at about 60 mg/L where TOC concentration in the effluent had been moreover increased due to decomposed products such as aldehydes and organic acids. Thus, further investigation is needed to see whether the bench scale (reactor volume, 8.9 L) of activated sludge could facilitate the decomposition of 1,4-dioxane and their by-products (i.e., TOC). As a result, 1,4-dioxane in the effluent has been decreased as low as 0.5 mg/L. The optimal conditions for the activated sludge process that were obtained are as follows: DO, 3-3.5 mg/L; HRT, 24 h; SRT 15 d; MLSS, 3,000 mg/L. Consequently, photo-Fenton oxidation coupled with activated sludge can make it possible to efficiently decompose 1,4-dioxane to keep up with that of the regulation standard.

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.

Activity of a Methanotrophic Consortium Isolated from Landfill Cover Soil: Response to Temperature, pH, CO2, and Porous Adsorbent

ABSTRACT A robust, naturally evolving methanotrophic community in landfill cover soil (LFCS) can be the simplest way to mitigate landfill methane emission. In this study, bacterial community composition in LFCS and methane oxidation potential of enriched methanotrophic consortium, in comparison to that of axenic Methylosinus sporium, was investigated. Growth and methane oxidation of the consortium was studied in liquid phase batch experiments under varying temperature (20–40°C), pH (5–10), headspace CO2, and in presence of porous adsorbent (1.3 cm3 sponge cubes). The 16S rRNA gene analysis revealed presence of both type-I and type-II methanotrophs along with few obligate methylotroph in LFCS. Though the optimal growth condition of the consortium was at 30°C and pH 7, it was more resilient in comparison to M. sporium. With increasing availability of porous adsorbent, methane consumption by the consortium was significantly improved (p < 0.001) reaching a maximum specific methane oxidation rate of 11.4 μmol mg−1 biomass h−1. Thus, inducing naturally thriving methanotrophs in LFCS is a better alternative to axenic methanotrophic culture in methane emission management.

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.

COMPARISION OF nirS, cnorB, MCR GENES AGAINST WATER QUALITY PARAMETERS TO MONITOR UNCONTROLLED LANDFILLS

Abstract This study was conducted to investigate the possible relationship between a molecular biological investigation and water quality parameters in monitoring groundwater pollution at the immediate boundary of uncontrolled landfills and their downgradient aquifers, which may consequently facilitate unbiased monitoring for the sites. Two closed landfills, Jicksan and Taejang in Korea, were chosen for this study, where the diversity of the microbial community was characterized and three specific genes, i.e. nirS (nitrite reductase coding gene), cnorB (nitric oxide reductase coding gene) and MCR (methyl coenzyme M reductase coding gene), were quantified. The quantified genes were then compared with conventional water quality parameters. From the analyzed DNA sequences, Proteobacteria phylum was most dominantly observed. A quantitative analysis revealed that the copy numbers (gene abundance) of denitrification enzyme coding genes, i.e. nirS gene and cnorB gene in Jicksan (J) site, are seven and four times, respectively, higher than Taejang (T) site. This simply implied that denitrification was possibly higher in J site than T site. In addition, a methane production enzyme coding gene, i.e. MCR, in a J1 bore immediately bordering the sources in the J site showed the greatest concentration, but it was precipitously decreased in the downgradient direction toward the outer boundary of landfill. A comparative investigation between the copy numbers of three genes, i.e. nirS, cnorB, and MCR, and conventional monitoring parameters, i.e. Cl−, alkalinity, TOC, NH3‐N, and NO2‐N, showed that they had overall correlation as given by more than 0.99 of the squared correlation coefficient (R 2) for almost all of the concerned bores. It was concluded that the comparison between the molecular biological investigation and the conventional groundwater monitoring parameters showed good relationship between them, so that both tools could be more efficiently used for assessing the levels of contamination and prediction of the fate of pollutants, rather than being applied separately.