• Korean Journal of Environmental Agriculture
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• v.21 no.4
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• pp.274-278
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• 2002

Nitrate removal rate in three wetland cells was examined. The acreage of each cell was 150 $m^2$. They were a part of a stream water treatment demonstration system which was composed of two ponds and six wetland cells. Earth works far the pond-wetland system were finished from April 2000 to May 2000 and reeds were planted in the three cells in May 2001. Waters of Sinyang Stream flowing into Kohung Esturiane Lake located southern coastal area of Korean Peninsula were pumped into a primary pont Effluents from a secondary pond were funneled into the three cells. Volumes and water quality of inflow and outflow were analyzed from July 2001 through December 2001. Inflow and outflow averaged 20 $m^3/d$ and 19.3 $m^3/d$, respectively. Hydraulic retention time was 1.5 days. Average influent and effluent nitrate concentration was 2.30 mg/L, 1.75 mg/L, respectively. Nitrate removal rate in the three cells averaged 80.9 $mg/m^2/day$. Seasonal changes of nitrate retention rates were closely related to those of wetland temperatures. Full growth of reeds within a few years can develope litter-soil substrates beneficial to the denitrification of nitrate, which may lead to increases of the nitrate retention rates.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2B
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• pp.187-192
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• 2011

Nitrate nitrogen is common contaminant in groundwater aquifers, its concentration is regulated many countries below 10 mg/L as N (As per WHO standards) in drinking water. An attempt was made to get optimal results for the treatment of nitrate nitrogen in groundwater by conducting various experiments by changing the experimental conditions for ZVI bipolar packed bed electrolytic cell. From the experimental results it is evident that the nitrate nitrogen removal is more effective when the reactor conditions are maintained in acidic range but when the acidic environment changes to alkaline due to the hydroxide formed during the process of ammonia nitrogen there by increasing the pH reducing the hydrogen ions required for reduction which leads to low effectiveness of the system. In the ZVI bipolar packed bed electrolytic cell, the packing ratio of 0.5~1:1 was found to be most effective for the treatment of nitrate nitrogen because ZVI particles are isolated and individual particle act like small electrode with low packing ratio. It is seen that formation of precipitate and acceleration of clogging incrementally for packing ratio more than 2:1, decreasing the nitrate nitrogen removal rate. When the voltage is increased it is seen that kinetics and current also increases but at the same time more electric power is consumed. In this experiment, the optimum voltage was determined to be 50V. At that time, nitrate nitrogen was removed by 94.9%.

• Journal of the Korean Applied Science and Technology
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• v.34 no.2
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• pp.217-224
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• 2017

This is a study on the removal of nitrate nitrogen from wastewater by oxidation and reduction reaction of zinc in an acidic atmosphere. The optimum removal rate of nitrate nitrogen and the optimum pH were studied by controlling the amount of zinc and sulfamic acid. The oxidation efficiency was higher at pH 2.0 in the range of pH 2.0 ~ 4.0 because the reaction occurred more strongly in strong acidic atmosphere. It is advantageous to reduce the nitrate ion to the final nitrogen gas by adding the sulfamic acid to the sulfurous acid because it consumes less $H^+$ ion than when the sulfamic acid is not present. According to the same amount of zinc, nitrate nitrogen was removed by 46.0% while sulfamic acid was not added, whereas nitrite nitrogen was removed by 93.0% by adding sulfamic acid. In addition, In this experiment, zinc was prepared in powder form and its reactivity was larger than that of other common zinc metal, so the removal efficiency was very high, about 80.0%, within one minute after the reaction.

• Journal of Soil and Groundwater Environment
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• v.10 no.1
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• pp.1-5
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• 2005

Nitrate reduction with zero valent iron $(Fe^0)$ has been extensively studied, but the proper treatment for ammonium byproduct has not been reported yet. In groundwater, however, ammonium is regarded as contaminant species, and particularly, its acceptable level is regulated to 0.5 mg-N/L. for drinking water. This study is focused on developing new material to reduce nitrate and properly remove ammonium by-products. A new material, Fe-loaded zeolite, is derived from zeolite modified by Fe(II) chloride followed by reduction with sodium borohydride. Batch experiments were performed without buffer at two different pH to evaluate the removal efficiency of Fe-loaded zeolite. After 80 hr reaction time, Fe loaded zeolite showed about $60\%$ nitrate removal at initial pH of 3.3 and $40\%$ at pH of 6 with no ammonium release. Although iron filing showed higher removal efficiency than Fe-loaded zeolite at each pH, it released a considerable amount of ammonium stoichiometrically equivalent to that of reduced nitrate. In terms of nitrogen species including $NO_3-N$ and $NH_4^+-N$, Fe-loaded zeolite removed about $60\%\;and\;40\%$ of nitrogen in residual solution at initial pH of 3.3 and 6, respectively, while the removal efficiency of iron filing was negligible.

• Journal of Environmental Science International
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• v.13 no.7
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• pp.675-680
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• 2004

This study was conducted to remove organics and nutrients using 2 stage intermittent aeration reactor. First reactor, using suspended microbial growth in intermittent aeration instead of anaerobic reactor in the typical BNR process, used minimum carbon source to release P, and it was possible to reduce ammonia loading going to second reactor. In the second reactor, using moving media intermittent aeration, it was effective to reduce nitrate in non-aeration time by attached microorganisms having long retention time. In aeration time, nitrification and P uptake were taken place simultaneously. From the experiment, two major results were as follows. First, the removal of organics was more than 90%, and optimum aeration/non-aeration time ratio for organic removal was corresponded with aeration/non-aeration time ratio for nitrogen removal. Second, in the first reactor, optimum aeration/non-aeration time ratio was 15/75 (min.) because it was necessary to maintain 75 min. of non-aeration time to suppress of impediment of return nitrate and to lead release of phosphate. In the second reactor, optimum aeration/non-aeration time ratio was 45/90 (min.).

• Ocean and Polar Research
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• v.26 no.1
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• pp.102-111
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• 2004

Recirculating aquaculture system (RAS) consists of different treatment compartments that maintain water quality within the ranges commonly recommended for fish cultures. However, common RASs still exert considerable environmental impact since concentrations of organic matter and nutrients in their effluents are high. Compared with the traditional RAS, the model RAS developed here use a sedimentation basin for digestion purposes and then use the released volatile organic matter to stimulate a denitrification process. Different treatment compartments for solids, total ammonia nitrogen, and nitrate removal have been reviewed. This paper provides the basic information on designing different treatment compartments as well as the engineering criteria in closed seawater RAS, consisting of circular tanks for fish cultures; dual drain systems, sedimentation basins and foam fractionators for removal of solids; nitrification biofilters for TAN removal; denitrification biofilters for nitrate removal; and aerators for aeration. The main purpose is to outline a common procedure in designing of closed RAS for marine fish culture with an emphasis on easy management and low expense, as well as reduction of the environmental impact.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.2
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• pp.135-142
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• 2021

The activity of anaerobic ammonium oxidation (ANAMMOX) immobilized in synthetic media (Poly Ethylene Glycol, PEG) and granular form was evaluated comparatively to investigate the effect of influent nitrogen concentration and exposure of oxygen. In ANAMMOX granule reactor, when concentration of influent total nitrogen increased to 500mg/L, removal efficiency of ammonium, nitrite and nitrate were shown to 90.5±6.5, 96.6±4.9, and 93.2±6.1%, respectively. In the case of the PEG gel, it showed lower nitrogen removal performance, resulting in that the removal efficiency of ammonium, nitrite and nitrate were shown to 83.3±13.0, 96.4±6.1, and 90.3±7.5%, respectively. In second step, when exposed to oxygen, the nitrogen removal performance in the ANAMMOX granule reactor also remained stable, but the activity of PEG gel ANAMMOX was found to be inhibited. Consequently, the PEG gel ANAMMOX was a higher sensitivity than that of granular ANAMMOX with two variables applied in this study.

• Journal of Bio-Environment Control
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• v.26 no.4
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• pp.393-401
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• 2017

The nitrate ($NO_3{^-}$) accumulation of hydroponically grown leafy vegetables may increase in the condition of a closed-type plant production system with low light intensity due to low activity of enzymes involved in nitrogen assimilation and the use of $NO_3-N$ as major nitrogen source. The objective of this study is to investigate the effects of light intensities, nutrient solution compositions and the time of nutrient solution removal before harvest on nitrate contents of hydroponically-grown lettuces in a closed plant production system. The reduction of nitrate contents in leafy lettuces 'Cheongchima' was higher in the treatments of 'TW' (nutrient solution removal) and '$(NH_4)_2CO_3$' (use of ammonium carbonate as nitrogen source) than those in other treatments, which significantly lowered fresh weight and leaf area of the plants. In the light intensity of $100{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, the nitrate content was effectively reduced without causing any growth retardation, by substitution of the nutrient solution composition that $NO_3-N$ was removed ('$NO_3-N$ removal' treatment) or the half strength of standard nutrient solution was applied ('1/2 S' treatment), for 7days before harvest. The effects of light intensity and the time of nutrient solution removal before harvest on growth and nitrate contents in leafy lettuces were investigated. The nitrate contents in leaves under the light condition of $300{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ before nutrient solution removal were lower than those of 100 or $200{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. The removal of nutrient solution for 7 days before harvest quickly reduced the amount of nitrates in leaves in all the light intensities with a greater degree under the $300{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ of light condition, while the 7 days-removal with both 200 and $300{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ of light conditions caused decrease in 16~31% of leaf area and 20~35% of fresh weight, compared to the 3 days-removal treatment. The nitrate contents were greatly reduced from 3,018 to 1,035 in $200{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, and 2,021 to 480 ppm in the light condition of $300{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, with the nutrient solution removal for 3 days before harvest, without causing any deterioration in growth and product quality. The vitamin C contents in leaves were higher in the treatment of nutrient solution removal for both 3 and 5 days before harvest with the light condition of $300{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ than those in the light condition of 100 or $200{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$.

• Journal of Environmental Science International
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• v.16 no.11
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• pp.1271-1277
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• 2007

This study was conducted to investigate the ratios of phosphorus release to COD uptake, phosphorus release to nitrate removal, and phosphorus uptake to phosphorus release by DNPAOs(denitrifying phosphate accumulating organisms). In case $I{\sim}IV$, influent 1 were fed with synthetic wastewater with influent 2 $NO_3^--N$ injection to anoxic zone and the case V were fed with municipal wastewater with side stream oxic zone instead of influent 2 $NO_3^--N$ injection. As a result, the ratio of phosphorus release to carbon uptake was increased in accordance with nitrate supply. The DNPAOs simultaneously took up phosphate and removed nitrate from the anoxic reactor. In case $I{\sim}IV$, with above 20 mg/L of sufficient $NO_3^--N$ supply, phosphate was taken up excessively by the DNPAOs in anoxic condition. The large amount of both uptake and release of phosphorus occurred above 20 mg/L of nitrate supply, achieving the ratio of phosphorus uptake to phosphorus release to be 1.05. In case V, phosphate luxury uptake was not occurred in system due to 6.98 mg/L of insufficient $NO_3^--N$ supply and the ratio of phosphorus uptake to phosphorus release was 0.98. Consequently, if nitrate as the electron acceptor was sufficient in anoxic zone, the ratio was found to be high.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.97-99
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• 2004

To understand the geochemical processes controlling the distribution of nitrate and other agricultural constituents in an alluvial aquifer, hydrogeological and hydro geochemical studies were carried out in an agricultural area within Cheonan. In this selected field, nitrate concentrations were very wide in range but was locally attenuated significantly down to very low levels (<1.0 mg/L). Abrupt removal of nitrate coincided with the pattern of redox change and thus indicated that geochemical processes occurring during and after recharge events control the behavior and distribution of nitrate and other redox-sensitive chemical species.