• Journal of Environmental Science International
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• v.24 no.4
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• pp.541-547
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• 2015

Formation of disinfection by-products (DBPs) including trihalomethans (THMs) and haloacetic acids (HAAs) from chlorination of six different species (Chlorella vulgaris, Scenedesmus sp., Anabaena cylindrical, Microcystis aeruginosa, Asterionella formosa and Aulacoseira sp.) of algal extracellular organic matter (EOM). The EOM characteristics evaluation of six algal species reaching at the stationary phase in the growth curve showed most of its SUVA254 showed below 1 and this means hydrophilic organic matter is much higher than hydrophobic organic matter. Chloroform formation potential (CFFP), dichloroacetic acid formation potential (DCAAFP) and trichloroacetic acid formation potential (TCAAFP) were mainly composed of THMFP and HAAFP in the EOM of various algal species. In the case of THMFP/DOC and HAAFP/DOC values, EOM of blue-green algae has appeared highest and EOM of green algae and diatom in order. THMFP/DOC was higher than HAAFP/DOC in EOM of blue-green algae. In comparison of formation potential by unit DOC composed of HAAFP in algal species EOM, DCAAFP/DOC was 1.5 times to 7.5 time higher than TCAAFP/DOC in the EOM of blue-green algae, while DCAAFP/DOC was found to be relatively high compared to TCAAFP/DOC in the EOM of green algae and diatom.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.4 no.2
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• pp.46-53
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• 1995

In this study, Wear of a ceramic cutting tool for hardened STD11 steel was investigated. Under the finish machining condition. DOC notch wear of a ceramic cutting tool was mostly occurred earlier than flank and crater wear were proceeded. The relations of DOC notch wear, which was characteristically produced at the beginning of cutting. to cutting speed, feed, depth of cut, and nose radius of a ceramic cutting tool were examined. Effective approach angle, which is a function of cutting conditions, and boundary area were suggested, and then the influence of those was investigated, The following conclusions were obtained: (1)as cutting speed was increasing. DOC notch wear was decreasing (2) the cutting condition that magnitude of slendermess ratio was made small, was favorable for DOC notch wear, (3) as depth of cut was smaller, the influence of feed on DOC notch wear was also smaller, (4) DOC notch wear was mainly influenced by effective approach angle, but by boundary area in the range of low feed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.1
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• pp.52-58
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• 2004

To develop a low emission engine, it is necessary to obtain some better quality of automotive fuels. Sulfur in fuel is transformed to sulfate-laden PM as DOC is applied. Therefore, it necessary to provide low sulfur fuels before DOC is applied. According to the specification of test fuels, flash point, distillation 90％, cetane index are improved but viscosity is decreased in the process of desulfurization. Excessively reduced sulfur may cause to decrease lubricity of fuel and engine performance in fuel injection system. Therefore, this research was emphasized how the application of Bio-diesel affects on the emission characteristics and engine performance under the circumstance of ULSD and DOC.

• Journal of Life Science
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• v.10 no.1
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• pp.14-21
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• 2000

The experiments were performed using both batch and continuous column reactors. Batch biodegradation studies were performed under aerobic conditions to determine the biodegradable fraction of the natural organic matter (NOM) source. NOM source was evaluated for its biodegradability at three different UV irradiation conditions and compared to its biodegradability without UV irradiation. In continuous experiments, system operating parameters of empty bed contact time (EBCT), recycle ratio, and influent concentration affected the extent of biofiltration in the biofilters. The effluent UV254/DOC ratios fro the biologically active columns were consistently lower than the influent values, which indicated that the dissolved organic carbon (DOC) removed by biodegradation was not a significant part of the UV-absorbable material. The increase in UV254/DOC ratio was caused by the DOC decrease across the biofilter because there was essentially no difference between the feed and effluent UV254 absorbance values over time. The results of this research showed that biofiltration was an effective method for removing the biodegradable fraction of NOM from water supplies.

• KSBB Journal
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• v.16 no.4
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• pp.332-336
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• 2001

This paper is intended as an application of the biological rope media sedimentation tank using biodegradability of BAC(Biological activated carbon) to the drinking water treatment system for the removal of NOM. The removal of DOC(Dissolved organic carbon), UV absorbance(UV$\_$254/), and turbidity were evaluated under various operation condition of a biological rope media sedimentation tank such as raw water-media process (Media 1), ozonation-media process (Media 2), and ozonation-coagulation/sedimentation-media process (Media 3). The raw water had DOC concentration of 1.3∼3.4 mg/L, UV$\_$254/ of 0.027∼0.039 cm$\^$-1/, and turbidity of 0.3∼4.5 NTU, respectively. The average DOC concentration were 2.2 mg/L in media 1, 1.8 mg/L in media 2, and 1.3 mg/l in media 3 from raw water, respectively. On the other hand, the DOC concentration in conventional sedimentation tank was 1.5 mg/l. Higher removal of the DOC was noted in media 3 than media 1 and media 2. The UV$\_$254/ of the treated water were 0.037 cm$\^$-1/ in media 1, 0.027 cm$\^$-1/ in media 2, and 0.014 cm$\^$-1/ in media 3 from raw water, respectively The UV$\_$254/ in conventional sedimentation tank was 0.014 cm$\^$-1/ which is similar to that of media 3. Average turbidity of the treated water was 1.1 NTU in media 1, 0.9 NTU in media 2, and 0.5 NTU in media 3, respectively. It is expected that the biological rope media sedimentation tank is a good alternative over the conventional sedimentation process from these results.

• Journal of Korean Society on Water Environment
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• v.29 no.1
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• pp.81-87
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• 2013

Changes of organic carbon after the entrance into dam reservoirs were investigated using water samples collected in May, September, and October in 2010 from the inflow sites and the outlets of four selected dam reservoirs-Soyang, Chungju, Chungju regulation, and Uiam. Increase of refractory dissolved organic carbon (R-DOC) was observed only for large dam reservoirs with long residence times whereas the trend was not found for relatively small reservoirs. The effects of residence times on organic carbon changes were further confirmed by significant positive correlations between monthly residence times and the relative increase of either dissolved organic carbon (DOC) or R-DOC concentrations. Comparison of spectroscopic characteristics of DOC revealed that the changes in the large reservoirs in May might result from in-lake processes. The inflow of terrestrial sources of DOM during storms appears to largely affect the DOC quality of the large reservoirs for the rest of the sampling periods. The mechanism, however, did not fully explain the behaviors of DOC for the small sized reservoirs. Our combined results suggested that both residence time and the input of allochthonous carbon sources might substantially influence the quantity of DOC as well as its quality in dam reservoirs.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.4
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• pp.419-424
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• 2007

According to increase of consumer's desire for clean tap water, advanced treatment processes include with membrane, ozone, and granular activated carbon(GAC) were introduced. In order to evaluate the effect of advanced treatment processes for residual chlorine decay and trihalomethane(THM) formation in water distribution system, dissolved organic matter(DOC) removal of each advanced treatment process was investigated. The residual chlorine decay and THM formation using bottle tests were also evaluated. $UV_{254}$ removal in all advanced treatment was better than DOC removal. Especially, DOC by ozone treated was removed as 4% in contrast with sand filtered water, but $UV_{254}$ was removed about 17%. This result might be due to convert from hydrophobic DOC to hydrophilic DOC by ozonation. Ozone/GAC process was most effective process for DOC removal. The residual chlorine decay constants in treated water by sand filtration, ozonation, GAC adsorption, and ozone/GAC processes were 0.0230, 0.0307, 0.0117 and 0.0098 $hr^{-1}$, respectively. The sand filtered water was produced 81.8 ${\mu}g/L$ of THM after 190 hours of reaction time, as the treated water by ozone, GAC, and Ozone/GAC was less produced 6.0, 26.2, 30.3% in contrast with sand filtered water, respectively. Consequently, the durability of residual chlorine and reduction of THM formation were improved by advanced treatment processes.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.12
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• pp.861-866
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• 2013

The aim of this study was to investigate the biodegradation of dissolved organic matter derived from animal carcass disposal soil using soil inhabited bacteria and to identify the bacteria involved in the biodegradation. The two soils were obtained from the animal carcass burial sites located in Anseong, Gyeonggi-do, Korea. The results indicated that during the biodegradation experiments (56 days), 48% of dissolved organic carbon (DOC) was mineralized within 13 days in soil-derived solution 1 (initial DOC = 19.88 mgC/L), and the DOC concentration at 56 days was $8.8{\pm}0.4$ mg C/L, indicating 56% mineralization of DOC. In soil-derived solution 2 (initial DOC = 19.80 mgC/L), DOC was mineralized drastically within 13 days, and the DOC concentration was decreased to $6.0{\pm}0.4$ mg C/L at 56 days (76% mineralization of DOC). Unlike DOC value, the specific UV absorbance ($SUVA_{254}$) value, an indicator of proportion of aromatic structures in total organic carbon, tended to increase until 21 days and then decreased thereafter. The $SUVA_{254}$ values in soil-derived solutions 1 and 2 were the highest at 21 days. The microbial analysis demonstrated that Pseudomonas fluorescens, Achromobacter xylosoxidans, Nocardioides simplex, Pseudomonas mandelii, Bosea sp. were detected at 14 days of incubation, whereas Pseudomonas veronii appeared as a dominant species at 56 days.

• Journal of environmental and Sanitary engineering
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• v.19 no.2
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• pp.1-6
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• 2004

In Bok-Jeong water treatment plant, chlorination is the only technique used for disinfection of drinking water. This disinfecting treatment leads to the formation of trihalomethanes (THMs). This study was carried out to investigate the possibility of improving removal efficiency of THM precursor in the conventional water treatment processes by $TiO_2$ photocatalytic oxidation. Removal efficiencies of DOC, $UV_{254}$, THMFP were low in the conventional water treatment processes. With application of $TiO_2$ photocatalyst, DOC, $UV_{254}$, THMFP were reduced more effectively. As the $TiO_2$ photocatalytic reaction time increased, the removal efficiencies of DOC, $UV_{254}$, THMFP were increased. The $TiO_2$ photocatalytic removal efficiencies of DOC, $UV_{254}$, THMFP were increased with increasing $TiO_2$ dosage. However, over 0.6g/l of $TiO_2$ dosage, the efficiency reached a plateau.

• Journal of Korean Society on Water Environment
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• v.39 no.2
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• pp.131-141
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• 2023

In this study, the relationship between organic carbon distribution characteristics and decomposition rate classified according to the particle size and biological degradation characteristics in water was investigated for the Nam river and Geumho river. The average concentrations of TOC in the Nam river and Geumho river were 2.7±1.2 mg/L and 5.0±1.2 mg/L, respectively, but the composition ratios for each type of organic carbon were similar. An average value of 80.9% of TOC was present as DOC and 72.8% of DOC consisted of Refractory-DOC (RDOC). In addition, the change in the RDOC composition ratio according to temporal and spatial distribution was the smallest. There was no difference in the decomposition rate of organic carbon except for TOC by the site (p≥0.108, one-way ANOVA), and the decomposition rates of Labile-POC (LPOC) and LDOC were similar at 0.139±0.102 and 0.137±0.149 day^-1, respectively (p=0.110, paired t-test). The coefficient of variation (CV) of the decomposition rate of DOC (average 8.1%), which had the smallest composition ratio of organic carbon, was 1.1, showing the largest temporal variation. The TOC, POC, and DOC decomposition rates showed a significant correlation with the ratio of the initial concentration to the concentration after 25 days of decomposition (OC₂₅/OC₀) (r²=0.89~0.94, p<0.001), and the decomposition rates of LPOC and LDOC were significantly correlated with the ratio of the initial concentration to the concentration after 5 days of decomposition (LOC₅/LOC₀) (r²=0.67~0.75). This suggests that it is possible to estimate the decomposition rate through the concentration of each type of organic carbon.