• Journal of Korean Society of Environmental Engineers
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• v.29 no.2
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• pp.220-228
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• 2007

In this study, effective simultaneous nitrification and denitrification reaction was accomplished in a completely mixed single bioreactor. As the important factors on the reaction, optimal DO concentration and effective range of influent C/N ratio was investigated with the synthetic wastewater. Experimental results show that stable nitrogen removals were accomplished with 0.5 mg/L DO concentration and over 7 C/N ratio. Nitrogen removal efficiency of the real municipal wastewater was low with 0.5 mg/L DO concentration because of its low C/N ratio. The increment of the C/N ratio at the inflow of the municipal wastewater with addition of external carbon source (glucose) over 7(up to 14) shows over 70% nitrogen removal in the single bioreactor.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.9
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• pp.997-1002
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• 2007

The objectives of this research are to remove dissolved organic matter and nitrogen compounds by using aerated submerged bio-film(ASBF) reactors in batch systems and improve understanding of dissolved organic matter and nitrogen compounds removal rates with dynamic relationships between heterotrophic and autotrophic bacteria in the fixed-film reactor. This research explores the possibility of enhancing the performance of shallow wastewater treatment lagoons through the addition of specially designed structures. These structures are designed to encourage the growth of a nitrifying bacterial bio-film on a submerged surface. Specially, the effects of cold temperatures on the dissolved organic matter and ammonia nitrogen performance of the ASBF pilot plant was investigated for the batch system. It is anticipated thai the ASBF would be used for a design of biological treatment for removing of dissolved organic matter and nitrogen compounds in new wastewater treatment plants as well as existing wastewater treatment plants.

• Korean Journal of Microbiology
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• v.46 no.1
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• pp.27-32
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• 2010

We used phototrophic bacteria to remove low concentrated organic materials (CODCr), nitrogen and phosphorus. We applied $COD_{Cr}$ 37.3 mg/L, $NH_3-N$ 4.0 mg/L, and $PO_4^{3-}-P$ 1.0 mg/L (C:N:P=100:10:1) in the batch test, and the removal efficiencies were shown as follow: $COD_{Cr}$ 87.4%, $NH_3-N$ 46.3%, $PO_4^{3-}-P$ 79.7%. The aerobic process with mixed phototrophic bacteria, ceramic media, and media KSP01 showed the removal efficiencies of $COD_{Cr}$, $NH_3-N$, and $PO_4^{3-}-P$, each as 72.7% and 79.2%, respectively in the lab-scale reactor. The maximum $PO_4^{3-}-P$ removal efficiency reached 92.6% by adjusting pH. There were three conditions used to remove $NH_3-N$. The highest removal efficiency was 98.5% with 10.2 L/min of aeration in 1-2 reactors, and the result of applying river-water showed the high removal efficiency of $NH_3-N$ (82.8%). Therefore, this purification system may be useful to control nitrogen and phosphorus at low concentration in field.

• Journal of Wetlands Research
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• v.19 no.1
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• pp.90-102
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• 2017

In this study, various types of nutrient models were tested by using two tears's water quality data collected from the stormwater wetland in Korea. Based on results, most important factor influencing nitrogen removal was hydraulic loading rate, which indicates that surface area of wetland is more important than its volumetric capacity, and model proposed by WEF was found to give a least error between measured and calculated values. For the phosphorus, in case assuming a power relationship between rate constant and temperature, the best prediction result were obtained, but temperature was most sensitive parameter affecting phosphorus removal. In addition, denitrification was always a limiting step for the nitrogen removal in this particular wetland mostly due to the lack of carbon source and high dissolved oxygen concentration. In this paper, several alternatives to improve nitrogen removal, including proper arrangement and designation of wetland elements and use of floating plants or synthetic fiber mat to control oxygen level and to capture the algal particles were proposed and discussed.

• Journal of the Korean Applied Science and Technology
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• v.33 no.4
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• pp.795-801
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• 2016

This study is on the denitrification process using the sodium alginate and $CaCl_2$ as a flocculant. Removal techniques of nitrate nitrogen from waste water are reverse osmosis, ion exchange, electro dialysis and biological method etc. We tried to remove nitrate nitrogen with flocculation and sedimentation method in the present study. Calcium alginate is expected to form a chelate bond with nitrate nitrogen in the solution. So the effects of flocculantt component, flocculation reaction time, molar ratio of the flocculant, flocculant injection rate are studied to determine the best removal rate of nitrate nitrogen. In addition, we tried to determine the nitrate nitrogen removal mechanism by analyzing the structure and component ratio of the configuration after the agglutination precipitate by FE-SEM and EDS. As a result, the nitrate nitrogen removal mechanism is turned out to form calcium-nitro-alginate, and the best mole ratio of flocculating agent is 1 : 1, the injection rate of the flocculant was up to 2%, the removal rate of the nitrate nitrogen to be 56.7% in the synthetic wastewater.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.355-361
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• 2006

In this study, effects of influent C/N(COD/Nitrate) ratio and dissolved oxygen(DO) concentration on biological nitrate removal from groundwater were investigated in the fixed-type biofilter. Influent nitrate of 30 mg/L was removed completely by biological denitrification at the C/N ratio of 10 and 4.0, while residual nitrate of 5 mg/L occurred at the C/N ratio of 2.0, which resulted from deficiency of organic electron donor. Furthermore, nitrite was accumulated up to about 5 mg/L as the C/N ratio decreased to 2.0. Increase in DO concentration also inhibited denitrification activity at the relatively high C/N ratio of 5.0, which decreased the nitrate removal efficiency. Although the influent DO concentration was reduced as low as 0.3 mg/L using sodium sulfite($Na_2SO_3$), effluent nitrite was up to 3.6 mg/L. On the other hand, nitrate was completely removed without detection of nitrite at the DO concentration of 0.3 mg/L using nitrogen gas($N_2$) sparging. The organic matter for denitrification in biofilter were in the range from 3.0 to $3.5gSCOD/g{NO_3}^--N$, while utilized these values increased at the high DO concentration of 5.5 mg/L. In addition to the high DO concentration and the low influent C/N ratio, DO control by chemical such as sodium sulfite affected on biological denitrification, which resulted in the reduction of nitrate removal efficiency and nitrite build-up in a biofilter.

• Clean Technology
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• v.28 no.4
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• pp.309-315
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• 2022

Research was conducted to derive the optimal operation conditions and the optimal cathode for using a DSA electrode as an anode to minimize electrode consumption during the removal of nitrogen from wastewater by the electro-chemical method. Of the various electrodes tested as cathodes, brass was determined to be the optimal electrode. It had the highest NO₃-N removal rate and the lowest concentration of residual NH₃-N, a by-product when Cl is present in the solution. Investigating the effect of current density found that when the initial concentration of NO₃-N was 50 mg L^-1, the optimal current density was 15 mA cm^-2. In addition, current densities above 15 mA cm^-2 did not significantly affect the NO₃-N removal rate. The effect of electrolytes on removing NO₃-N and minimizing NH₃-N was investigated by using Na₂SO₄ and NaCl as electrolytes and varying the reaction times. When Na₂SO₄ and NaCl are mixed at a ratio of 1.0 g L^-1 to 0.5 g L^-1 and reacted for 90 min at a current density of 15 mA cm^-2 and an initial NO₃-N concentration of 50 mg L^-1, the removal rate of NO₃-N was about 48% and there was no residual NH₃-N. On the other hand, when using only 1.5 g L^-1 of NaCl as an electrolyte, the removal rate of NO₃-N was the highest at about 55% and there was no residual NH₃-N.

• Journal of Wetlands Research
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• v.18 no.3
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• pp.244-249
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• 2016

Anaerobic digester supernatant including high concentrations of nitrogen is recycled to water treatment line and make pollutant load increase in municipal wastewater treatment plant(MWTP). To treat nitrogen in anaerobic digester supernatant is suggested the method of MWTP retrofit. In this study, the lab scale reactor was operated about 200 days using supernatant of anaerobic digester. The results could draw operation condition that ammonium nitrogen removal efficiency more than 90% and nitrite conversion efficiency over 70%. Correlation between operation efficiency and operation factors was analyzed based on the operation results. Ammonium nitrogen remove efficiency and nitrite conversion efficiency were related to solid retention time (SRT), ammonium nitrogen load and ammonium nitrogen loading per unit mixed liquer suspended solid (MLSS). Results of this study can be used effective data on nitritation of supernatant of anaerobic digester, and be expected to increase availability of nitritation.

• Microbiology and Biotechnology Letters
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• v.26 no.1
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• pp.76-82
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• 1998

The feasibility of algae as means of removing nitrogen and phosphorus from secondary treated swine wastewater was studied. Among the tested 7 species of Chlorella vulgaris (UTEX 265), Chlorella sp. GE 21, Botryococcus braunii (UTEX 572), Botryococcus sp. GE 24, Scenedesmus quadricauda, Phormidium sp. GE 2, and Spirulina maxima (UTEX 2342), C. vulgaris was selected for its fast growth and abilities to remove nitrogen and phosphorus and to produce algal biomass from swine wastewater. C. vulgaris grew well at 35$^{\circ}C$, and the optimum initial pH for growth was 8.0. In the effect of light intensity, the growth of C. vulgaris was limited under a light intensity of less than 40 ${\mu}$E/$m^2$/s. The secondary treated swine wastewater contained 58.7 mg/l of total nitrogen and 14.7 mg/l of total phosphorus, and was diluted to 75, 50, and 25% with groundwater to be treated. Nitrogen and phosphorus were removed by C. vulgaris in all diluted swine wastewaters among which the most effective removal was in 75% swine wastewater (swine wastewater:groundwater=3:1). There was a tendency of linear increase in nitrogen and phosphorus removal time with increasing concentration of swine wastewater. Under the optimized culture condition, total nitrogen and total phosphorus were effectively removed to 95.3% and 96.0%, respectively, in 25% swine wastewater after 4-day incubation.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.599-607
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• 2000

In this research, ${NH_4}^+-N$ and ${PO_4}^{3-}-P$ in wastewater were removed by crystallization. Nitrogen and phosphate have been regarded as key nutrients in the eutrophication of rivers and lakes. Struvite, $MgNH_4PO_4{\cdot}6H_2O$, is insoluble in alkaline solutions. Fertilizer industry wastewater contains organic and nitrogen concentration of 330 mg/L and 550 mg/L, respectively. Nitrogen in this wastewater cannot be treated by conventional biological treatment without physicochemical pretreatment, because nitrogen concentration is relatively high compared to organic concentration. Magnesium ions used in this study were from bittern and commercial magnesium salts of $MgCl_2$ and $Mg(OH)_2$. Bittern obtained as a by-product of seasalt manufacture contains $8,000mg\;Ca^{2+}/L$ and $32,000mg\;Mg^{2+}/L$. Optimum initial pH was 10.5~11.0 and the reaction was complete or done in 2 min. Nitrogen removal efficiency using bittern, $MgCl_2 $ and $Mg(OH)_2$ (as source of $Mg^{2+}$) was 71 %, 81% and 83%. respectively. Phosphate removal efficiency was 99%, 98% and 93%, respectively. Therefore, bittern, $MgCl_2$ and $Mg(OH)_2$ can be efficiently used as $Mg^{2+}$ source for crystallization of nitrogen and phosphate. However, bittern is economically favorable $Mg^{2+}$ source for removing nitrogen and phosphate in wastewater.