• Journal of Korean Society on Water Environment
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• v.24 no.1
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• pp.123-128
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• 2008

The Dissolved Organic Carbon (DOC) existing in a water includes both hydrophobic and hydrophilic substances however, most of the discussion focuses on hydrophobic substances. The hydrophobic fraction was easily removed by absorption or coagulation more than hydrophilic fraction. Therefore, control of the hydrophilic fraction is very important in water treatment process. This study is to determine the variation of DOC, the removal efficiency of DOC, and Trihalomethane formation potential (THMFP) after each stage of water treatment process by fractionating Natural Organic Matters (NOM) into hydrophobic and hydrophilic substance. DOC from raw water was fractionated at acidic pH (pH<2) using XAD 8 resin column, into two fraction : hydrophobic substance (i.e. humic substance) adsorbed on XAD 8 and hydrophilic substance which represent the organics contained in the final effluent. THMFP was carried out according to the following set condition: Cl2/DOC=4 mg/mg, incubation at $25^{\circ}C$ in darkness, pH 7 adjust with HCl or NaOH as necessary, and 72hour-contact time. THMs analyzed in this study were chloroform, bromodichloromethane, dibromochloromethan, and bromoform. Sewage was almost evenly split between the hydrophobic (56%) and hydrophilic fraction (44%). But, Aldrich humic substance (AHS) was found to contain less hydrophilics (14%) than hydrophobics (86%). The formation of THMs may depend on the source which is characterized by the composition of organic matters such as AHS and sewage. The THMFP yield of sewage and AHS were assessed as follows. The value of the THMFP reaction yield, AHS $172.65{\mu}g/mg$, is much higher than that of sewage $41.68{\mu}g/mg$. This illustrates possible significant difference in THMFP according to the component type and the proportion of organic matter existing in water source. Apparently AHS react with chlorine to produce more THMFP than do the smaller molecules found in sewage. Water treatment process may reduce THMFP, nevertheless residual DOC (the more hydrophilic substance) has significant THMFP. Further reduction in organic halide precursors requires application of alternative treatment techniques.

• Journal of the Korea Organic Resources Recycling Association
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• v.11 no.1
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• pp.70-76
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• 2003

Continuous anaerobic hydrogen production with a mixed culture was investigated. With a sucrose concentration of 5g COD/L in the feed, hydrogen production exceeded $0.5mole\;H_2/mole\;hexose$ was found at the early stage, however it did not maintain longer than 9days. It was assumed that the failure was caused by insufficient active hydrogen producing bacteria in the reactor. Therefore, effects of pH control, repeated heat treatment and substrate concentration on sustainable continuous anaerobic hydrogen production was examined to find out operating conditions to sustainable hydrogen production. Decrease of hydrogen production was not overcome by only pH control at 5.3. Repeated heat treatment could recover hydrogen producing activity without any external inoculum supply. However, frequent heat treatment was needed because the treated sludge also showed the tendency in decrease of hydrogen production. With a sucrose concentration of 30g COD/L in the feed, hydrogen production maintained $1.0-1.4mole\;H_2/mole\;hexose$ in continuously stirred tank reactor and $0.2-0.3mole\;H_2/mole\;hexose$ in anaerobic sequencing batch reactor) for 24days. More than 90% of soluble organics in effluent was organic acids, in which n-butyrate was the most one.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.10
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• pp.1024-1030
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• 2006

Genus Nitrospira and Nitrobacter species are the key nitrite-oxidizing bacteria(NOB) in nitrifying wastewater treatment plants. It has been hypothesized that genus Nitrospira are K-strategists(low $K_6$ value) that can exploit low amounts of nitrite more efficiently than Nitrobacter. In contrast, Nitrobacter species are r-strategists(high $V_{max}$) that can grow faster than Nitrospira. It has also been known that the availability of organic compounds and dissolved oxygen as well as nitrite affects the distribution of NOB. In this study, we determined the distribution and competition of NOB in wastewater nitrification systems where nitrite, organic compounds, and dissolved oxygen concentrations were compositively varied. For the purpose, several compounds of the laboratory-scale nitrificaiion bioreactor and full-scale $A_2O$ wastewater treatment plant and their distribution of NOB were analyzed and compared. The analysis showed that Nitrobacter was the dominant NOB in nitrification bioreactor where average nitrite was maintained at 5 mg-N/L with very low organic concentration in aerobic condition, whereas Nitrospira was the dominant NOB in full-scale $A_2O$ plant where nitrite was maintained very low and organic compounds were maintained relatively high in alternating aerobic-anoxic condition. The result indicates that nitrite concentration is more critical factor than organics and dissolved oxygen which determines the dominant NOB in nitrification system and it is confirmed that Nitrospira and Nitrobacter showed the characteristics of r-strategist and K-strategist, respectively.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.7
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• pp.738-745
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• 2006

In this research, the decolorization mechanisms of dye wastewater were divided into two pathways, one was physicochemical sorption to biomass flocs and the other was biological removal by microbial metabolisms. Batch tests were conducted to examine the reaction conditions, anaerobic and aerobic conditions, types and dose of cosubstrates, and to confirm the mechanisms of decolorization through the biosorption tests using the activated sludge and the autoclaved deactivated sludge. From the tests, the decolorization efficiencies of dye wastewater were 102 ${\Delta}$unit/g MLSS under the aerobic condition and 123 ${\Delta}$unit/g MLSS under the anaerobic condition, and organic removals were 82 $mg{\Delta}$COD/gMLSS and 75 $mg{\Delta}$COD/gMLSS respectively. Acetate was the more efficient cosubstrate than the domestic wastewater in the decolorization step. In addition the removal of colors and organics was increased with cosubstrates dosage. And $20.3{\sim}37.3$ ${\Delta}$unit/g MLSS was removed by the autoclaved sludge and $102.0{\sim}159.0$ ${\Delta}$unit/g MLSS by the activated sludge. The physicochemical sorption was dominant in the beginning of biosorption tests, and the biological decolorization was increased with a cosubstrate in the course of time.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.286-291
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• 2006

We studied possibility of mixing treatment of livestock wastewater and sewage using Phanerochaete chrysosporium PSBL-1. Our study showed that 97.6% of SS and 95% of T-P removal efficiency was achieved when 2 mL BF02(a coagulant) and 100 mL C-210EL(a cationic polymer) were added to the mixture(2:1, v/v) of livestock wastewater and sewage. We studied treatment characteristic of Phanerochaete chrysosporium PSBL-1, after were mixed pretreated wastewater and sewage by dillution ten times about livestock wastewater. The removal efficiency of NBDCOD(non-biodegradable COD), $NH_3-N$ and T-N was increased according to increase of pH. That is, T-N concentration of effluent was satisfied 60 mg/L by drain water waterqulity standard of livestock wastewater public treatment facilities with 35 mg/L from a lapse of five days at pH 6.7, 51 mg/L from a lapse of three days at pH 8 and 33 mg/L from a lapse of one day at pH 10. Moreover $COD_{Mn}$ concentration of effluent was satisfied 40 mg/L by drain water waterqulity standard of livestock wastewater public treatment facilities after a laps of one day at all pH. Organics and nitrogen concentrations of effluent were higher case with addition of V.A.(veratryl alcohol) than case without addition of V.A.(veratryl alcohol). $COD_{Mn}$ concentration of effluent satisfied drain water qulity standard of livestock wastewater public treatment facilities from a lapse of one day, when C/N rate(3:1) of influent was not controled. T-N satisfied that from a lapse of two days, when C/N rate was controled with $4{\sim}6$.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.2
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• pp.206-214
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• 2005

This study was initiated to evaluate efficiencies of suspenced-growth processes(CAS; Conventional Activated Sludge, MLE; Modified Ludzack-Ettinger) and hybrid process(Modified-Dephanox) on removal of organic matter(C), nitrogen(N) and phosphorus(P) in municipal wastewater. M-Dephanox process was designed to improve the performance of Dephanox process on denitrification efficiency. As the results, removal efficiencies of total chemical oxygen demand(TCOD), total nitrogen(T-N) and total phosphorus(T-P) in M-Dephanox process, which is hybrid process, were 12,3, 18.6 and 28.2% higher than those in MLE, which is suspended-growth process. The better removal efficiencies of TCOD, T-N and T-P in M-Dephanox than those in MLE result that M-Dephanox is not only hybrid or multi-sludge process but also process using biosorption mechanism which is possible to use organics in denitrification, effectively. Ammonia removal efficiency in nitrification reactor of M-Dephanox was 96.7% at short hydraulic retention time(HRT) of 2 hr which was 3 hr more short HRT than that(HRT 5 hr) reported in other related papers. This indicates that M-Dephanox process can reduce HRT of whole process.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.9
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• pp.851-856
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• 2010

A sulfur utilizing nitrite denitrification process could be placed after the shortcut biological nitrogen removal (SBNR) process. In this study, removal of nitrite using sulfur oxidizing denitrifier was characterized in batch tests with granular elemental sulfur as an electron donor and nitrite as an electro acceptor. At sufficient alkalinity, initial nitrite nitrogen concentration of 100 mg/L was almost completely reduced in the batch reactor within a incubation time of 22 h. Sulfate production with nitrite was 4.8 g ${SO_4}^{2-}/g$ ${NO_2}^-$-N, while with nitrate 13.5 g ${SO_4}^{2-}/g$ ${NO_3}^-$-N. Under the conditions of low alkalinity, nitrite removal was over 95% but 15 h of a lag phase was shown. For nitrate with low alkalinity, no denitrification occurred. Sulfate production was 2.6 g ${SO_4}^{2-}/g$ ${NO_2}^-$-N and alkalinity consumption was 1.2 g $CaCO_3/g$ ${NO_2}^-$. The concentration range of organics used in this experiment did not inhibit autotrophic denitrification at both low and high alkalinity. This kind of method may solve the problems of autotrophic nitrate denitrification, i.e. high sulfate production and alkalinity deficiency, to some extent.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.10
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• pp.927-932
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• 2009

Toxic and recalcitrant organic pollutants in wastewaters can be effectively treated when advanced oxidation and biodegradation are combined, ideally with intimate coupling, in which both processes occur simultaneously in the same system. One means to achieve intimate coupling is to coat nanoscale $TiO_2$ on the outside of macroporous biofilm carriers. This study investigated the kinetics of photocatalysis with $TiO_2$-coated porous carriers. The carriers were made of polyvinyl alcohol (PVA) and coated with $TiO_2$ using a low-temperature sol-gel process. The $TiO_2$-coated carriers catalyzed the oxidation of methylene blue (MB) effectively under irradiation of UV light. The overall reaction rate with adsorption and photolysis saturated at high MB concentration, and approached the adsorption rate, which was first order for all MB concent rations. This result indicates that adsorbed MB may have slowed photocatalysis by blocking active sites for photocatalysis. The overall kinetics could be described by a quasi-Langmuir model. The estimated maximum specific (per unit mass of $TiO_2$) transformation rate of MB by the $TiO_2$-coated carriers was four times larger than that obtained from slurry-$TiO_2$ reactors. This observation demonstrated that the $TiO_2$ present as a coating on the carriers maintained high efficiency for transforming recalcitrant organic matter via photocatalysis. These findings serve as a foundation for advancement of an intimate coupling of photocatalysis to biodegradation.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.5
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• pp.277-284
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• 2015

In order to analyze the contamination level of sediment samples taken from Chusori and Chudong areas in Daechung Reservoir, the particle size and concentrations of organics and nutrients were analyzed and phosphorus fractionation analysis was conducted. The average fraction of silt-sized particles was 92% in the sediments taken from Chudong area and Chusori area at the site adjacent to main current, which was higher than that from the upper Chusori area. The concentrations of total phosphorus in the sediments at Chusori and Chudong area were 999 (${\pm}98$) and 1,123 (${\pm}119$) mg/kg sediment, respectively. The fractions of autochthonous phosphorus, which can be readily eluted by change of environmental conditions, were much higher than those of allochthonous phosphorus, indicating the internal load can contribute the eutrophication in these areas. The concentrations of total nitrogen were over 5,600 mg/kg sediment in all samples, which is the guideline of Contamination Assessment of River and Lake Sediments of the Ministry of Environment, indicating the contamination level of total nitrogen is serious in the sediments. It is concluded that the countermeasures to manage the quality of sediments are required to improve the water quality in the Daechung Reservoir.

• Journal of Environmental Health Sciences
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• v.28 no.1
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• pp.51-65
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• 2002

This study was carried out to apply some basic physical and chemical treatment options including Fenton's oxidation, and to evaluate the performances and the characteristics of organic and nitrogen removal using lab-scale biological treatment system such as complete-mixing activated sludge and sequencing batch reactor(SBR) processes for the treatment of leachate from a municipal waste landfill in Gyeongnam province. The results were as follows: Chemical coagulation experiments using aluminium sulfate, ferrous sulfate and ferric chloride resulted in leachate CO $D_{Cr}$ removal of 32%, 23% and 21 % with optimum reaction dose ranges of 10,000～15,000 mg/$\ell$, 1,000 mg/$\ell$ and 500～2,000 mg/$\ell$, respectively. Fenton's oxidation required the optimum conditions including pH 3.5, 6 hours of reaction time, and hydrogen peroxide and ferrous sulfate concentrations of 2,000 ～ 3,000 mg/$\ell$ each with 1:1 weight ratio to remove more than 50% of COD in the leachate containing CO $D_{Cr}$ between 2,000 ～ 3,000 mg/$\ell$. Air-stripping achieved to remove more than 97% of N $H_3$-N in the leachate in spite of requiring high cost of chemicals and extensive stripping time, and, however, zeolite treatment removing 94% of N $H_3$-N showed high selectivity to N $H^{+}$ ion and much faster removal rate than air-stripping. The result from lab-scale experiment using a complete-mixing activated sludge process showed that biological treatability tended to increase more or less as HRT increased or F/M ratio decreased, and, however, COD removal efficiency was very poor by showing only 36% at HRT of 29 days. While COD removal was achieved more during Fenton's oxidation as compared to alum treatment for the landfill leachate, the ratio of BOD/COD after Fenton's oxidation considerably increased, and the consecutive activated sludge process significantly reduced organic strength to remove 50% of CO $D_{Cr}$ and 95% of BO $D_{5}$ . The SBR process was generally more capable of removing organics and nitrogen in the leachate than complete-mixing activated sludge process to achieve 74% removal of influent CO $D_{Cr}$ , 98% of BO $D_{5}$ and especially 99% of N $H_3$-N. However, organic removal rates of the SBR processes pre-treated with air-stripping and with zeolite were not much different with those without pre-treatment, and the SBR process treated with powdered activated carbon showed a little higher rate of CO $D_{Cr}$ removal than the process without any treatment. In conclusion, the biological treatment process using SBR proved to be the most applicable for the treatment of organic contents and nitrogen simultaneously and effectively in the landfill leachate.e.