• Journal of Korean Society of Environmental Engineers
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• v.29 no.8
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• pp.922-929
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• 2007

The complete oxidation of ammonia to nitrate is a distinctive two-step process divided into the oxidation of ammonia to nitrite(nitritation) by Nitrosomonas and the oxidation of nitrite to nitrate(nitratation) by Nitrobacter. The nitrogen removal via nitrite accumulation offers several advantages such as saving costs for aeration, saving carbon source and finally reduction of sludge discharge. In this work a suspended bioreactor coupled with membrane filtration(MBR) was used to find the process conditions of nitrite build-up. The MBR enables to reach sufficient nitrifying bacteria in the bioreactor, although the autotrophic bacteria can be easily washed out due to their lower growth rate. The dissolved oxygen concentration $c'_{O2}$ and ammonia concentration $c_{NH3}$ in the reactor were varied and investigated as parameters for nitrite accumulation. As a result the higher ammonia concentration in the reactor is very effective for starting nitrite build-up and the effect was strengthened in combination with lower dissolved oxygen concentration. With lower $c'_{O2}<0.3$ $mgL^{-1}$ $O_2$ and high $c_{NH3}=6.3\sim14.9$ $mgL^{-1}$ $NH_3N$ the 74% of the nitrite accumulation was achieved. Specially, it was found that the nitrite accumulation could occur not only in biofilm reactor as many references showed but also in the membrane bioreactor carried out in this study.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.1
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• pp.57-63
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• 2013

A combined process consisted of a biofilm reactor and a continuously stirred-tank reactor (CSTR) was investigated for highly loaded ammonium wastewater treatment via nitrite accumulation. To enhance ammonium oxidizing bacteria over nitrite oxidizing bacteria on the surface of carriers, the biofilm reactor was operated at temperature of $35^{\circ}C$ for more than three months but the influent ammonium (500 mg-N/L) was partially oxidized to nitrite (240 mg-N/L). As pH was increased from 7.5 to 8.0, nitrite accumulation was fully achieved due to the inhibition of nitrite oxidizing bacteria under high free ammonia concentration. The biofilm reactor performance was severely deteriorated at the hydraulic retention time of 12 hr, at which incomplete nitrification of ammonia was observed. Various solubilization methods were applied to sewage sludge for enhancing its biodegradability and the combined method, alkaline followed by ultrasonic, gave the highest solubilization efficiency (58%); the solubilized solution was used as the external carbon source for denitrification reaction in CSTR. FISH analysis showed that the dominant microorganisms on the carriers were ammonium oxidizing bacteria such as Nitrosomonas spp. and Nitrospirar spp. but low amounts of nitrite oxidizing bacteria as Nitrobacter spp. was also detected.

• Journal of environmental and Sanitary engineering
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• v.13 no.2
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• pp.128-138
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• 1998

This study was focused to find how each factors effect on the biological nitrification in wastewater treatment under high ammonia nitrogen concentration. Batch reactors in aerobic conditions were used to test the treatment efficiency of mixed liquor, nightsoil and piggery wastewater. The results are summeried as follows; Initial ammonia nitrogen concentration and pH were the direct influencing factors of nitrite build-up. More than 250 mg NH$_{4}$$^{+}$ - N/L in initial concentration built up nitrite and then the inhibition rate to Nitrobacter was above 70 percentage. And maximum nitritation rate was showed at pH 8.3 and nitrification could be completely achieved by pH control. Temperature and dissolved oxygen were the indirect influencing factors of nitrite build-up. These were a great effect on the activity of nitrifying microbes and ammonia nitrogen removal. Maximum nitritation rate was showed at 30 $\circ $C. The effect of DO concentration was negligible at more than 3 mg/L.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.5
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• pp.861-867
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• 2000

The feasibility of simultaneous phosphorus and nitrogen removal by enhancing anoxic phosphorus uptake was investigated in a sequencing batch reactor (SBR). By introducing an anoxic phase into an anaerobic-aerobic SBR (AO SBR), significant amounts of denitrifying phosphorus accumulating organisms (DPAOs) which can utilize nitrate as electron acceptor could be accumulated in the reactor (anaerobic-aerobic- anoxic-aerobic SBR, $(AO)_2$ SBR). A direct comparison of phosphorus uptake rate under anaerobic and aerobic conditions showed that the fraction of DPAOs in P-removing sludge were increased from 10% in the AO SBR to 64% in $(AO)_2$ SBR. The $(AO)_2$ SBR showed stable phosphorus and nitrogen removal efficiency: average removal efficiencies of TOC, total nitrogen, and phosphorus were 92%, 88%, and 100%. respectively. Results of the $(AO)_2$ SBR operation and batch tests showed that nitrite (up to 10 mg-N/L) was not detrimental to anoxic phosphorus uptake and could serve as good electron acceptor like nitrate.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.1
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• pp.51-62
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• 2010

The high concentration of N in the wastewater from livestock farming generally renders the efficiency of the wastewater treatment. Therefore, removal of N in livestock wastewater is crucial for successful treatment. The current study was conducted to investigate the optimum conditions for partial nitrification under anaerobic condition following nitritation in TPAD-BNR(two-phase anaerobic digestion-biological nitrogen removal) operating system. Sequential operating test to stimulate partial nitrification in reactor showed that partial nitrification occurred at a ratio of 1.24 in $NO_2{^-}$-N:$NH_4{^+}$-N. With this result, a wide range of factors affecting stable nitritation were examined through regression analysis. In the livestock wastewater treatment procedure, the hydraulic retention time (HRT) and pH range for optimum nitrite accumulation in the reactor were 1-1.5 days and 7-8, respectively. It was appeared that accumulation of $NO_2{^-}$-N in the reactor is due to inhibition of the $NO_2{^-}$-N oxidizer by free ammonia (FA) while the effect of free nitrous acid was minimal. Nitrification was not influenced by DO concentration at a range of 2.0-3.0 mg/L and the difference in the growth rate between $NH_4{^+}$-N oxidizer and $NO_2{^-}$-N oxidizer was dependent on the temperature in the reactor.

• Journal of Nutrition and Health
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• v.10 no.4
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• pp.111-115
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• 1977

Vegetables and fruits purchased from several markets in Seoul from July to October in 1977 were analyzed to know the level of nitrate-and nitrite-nitrogen accumulation in relation to a public health. Radishes and chinese cabbages utilized mainly as pickled vegetables in Korea resulted in the highest concentration of nitrate-nitrogen. Some of the levels for radishes and chinese cabbages were notably high and exceeded a recommended upper limit of 300 ppm $No_{3}-N$, and thus these levels would render these samples unsafe for use. The levels in some of vegetables other than radish and chinese cabbage, e.g., spinach, lettuce, green onion, cabbage were relatively high and considered to be unsafe for use in feeding infants, where as those of green pepper, bean sprouts and parsely were very low and safe. And also the levells in fruits were very low and safe. Nitrite-nitrogen contents in all tested vegetables and fruits ranged to trace and appeared not to be accumulated in fresh vegetables and fruits. Stems and roots of radishes and chinese cabbages accumulated approximately 2 fold more nitrate-nitrogen than leaves in 5 samples of each vegetable tested.

• Journal of Korean Society of Water and Wastewater
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• v.13 no.1
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• pp.51-60
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• 1999

An intermittently-aerated, intermittently-decanted single-reactor process (KIDEA process : KIST intermittently decanted extended aeration process) was applied for nitrogen removal from wastewater. Synthetic wastewater with chemical oxygen demand (COD): nitrogen (N) ratio of approximately 5.25: 1 was used. The average COD removal efficiency reached above 95%, and under optimal conditions nitrogen removal efficiency also reached above 90%. This process consisted of 72 minute aeration, 48 minute settling and 24 minute effluent decanting with continuous feeding of influent wastewater from the bottom of the reactor, and did not require a separate anoxic mixing-phase. In this process, nitritation ($1^{st}$ step of nitrification) was induced but nitratation($2^{nd}$ step of nitrification) was suppressed. Main factors responsible for the accumulation of nitrite ion in the experimental condition were free ammonium and dissolved oxygen. This condition of nitrite build-up accelerated by continuous feed flow in the bottom of the KIDEA reactor because of high concentration of ammonia nitrogen in the influent. This research provides one of answers to control nitrate build-up.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.9
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• pp.675-680
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• 2013

This research was done to evaluate the potential for destruction of perchlorate in municipal sewage. Laboratory experiments were conducted in flasks containing 3 liters of raw sewage. Sewage was mixed with defined amount of perchlorate and various additives. Perchlorate reduction in sewage did occur, but was quite variable, ranging from 0 to 72% over 72 hour. Addition of even a small amount of perchlorate acclimated biomass (167 mg/L SS) significantly reduced the lag and resulted in complete perchlorate removal. Perchlorate reduction in sewage-brine mixtures was inhibited when the dissolved oxygen level was greater than 2 mg/L, and when the mixture salinity was relatively high (conductivity = 14 mS with equivalent TDS = 8 g/L). When nitrate ($NO_3{^-}$) was present with perchlorate in the laboratory flask tests of sewage-brine mixtures, nitrate reduction proceeded first. A significant amount of nitrite ($NO_2{^-}$) accumulated in the sewage-brine mixtures, accounting for about 66% of initial nitrate nitrogen ($NO_3$-N).

• Korean Journal of Food Science and Technology
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• v.33 no.5
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• pp.507-513
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• 2001

An effective extraction methods of a garlic were investigated in order to improve the functional properties of the extracts. The solid yield, electron donating ability (EDA), nitrite-scavenging effects (NSE), peroxide value (POV) and total thiosulfinates contents of garlic extracts were determined. In order to improve the functional properties of extracts prepared with several organic solvents and acids, concentration and pH adjustment of the selected solvent and addition of acids and salts to solvents were also examined. Among the solvents tested, the methanol and ethanol extracts were found to be the most effective on the base of functionality and solid yields. The highest EDA, NSE and thiosulfinate value were obtained with 50% ethanol. The pH control of solvent and addition of citric acid, NaCl and phosphates to 50% ethanol did not affect on the functionality of the extracts. Therefore the optimal solvent for the best functional properties of garlic extract was 50% ethanol.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.1
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• pp.25-33
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• 1998

Temporal and spatial variations of nutrient elements (ammonia, nitrate, nitrite, phosphate and silicate) in surface seawater off the west coast of Korea were investigated during three periods of field survey aboard R/V Eardo of KORDI (May 1995 and June 1996) and a patrol vessel of the National Maritime Police (November 1995). In general, the concentrations of nutrient elements were lowest in June and highest in November except for ammonia that showed the lowest concentration in May and the highest in November. The results tell us that the development of thermocline and tidal front restricts riverine and benthic supply of nutrient elements to surface waters in June in the offshore regions of the study area which become nutrient-depleted due to phytoplankton bloom in spring. In late fall (November) the level of nutrient concentrations of the surface waters of the study area become high due to vigorous vertical mixing within the water column, which supplies nutrient-enriched bottom water to the surface waters.