• Journal of Korean Society of Environmental Engineers
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• v.30 no.2
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• pp.199-206
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• 2008

Simultaneous nitrification and denitrification means that nitrification and denitrification occur concurrently in the same reaction vessel under low DO concentration. Some mathematical models developed to simulate simultaneous nitrification and denitrification reaction, but they have the complex model structures or have limitations of model application. To solve these problems, if possible that predict the behavior of simultaneous nitrification and denitrification reaction by activated sludge model, structures of the model is less complex than previous models and applies the various operation conditions. But original activated sludge models have difficulties in representing the denitrification reaction under aerobic condition. So the aim of this study is to interpret simultaneous nitrification and denitrification reaction by modifying activated sludge model. Original activated sludge model No.1(ASM1) was selected and modified. The simulation result in modified ASM1 predicted appropriately for the measured data. This indicates the structures of ASM1 are properly improved for interpretation of simultaneous nitrification and denitrification reaction.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.10a
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• pp.213-214
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• 2000

총 암모니아성 질소(TAN)은 고밀도 양식에서 한계요소로 작용하는 수질인자 중의 하나이다. 생물학적 처리법에 의한 암모니아의 제거는 순환여과식 양식 시스템의 설계에서 가장 중요한 부분이다. 효율적인 순환 여과식 양식 시스템을 위해서는 생물반응기의 질산화 속도식을 구하여 적정한 용량의 처리시스템을 설계하여야 한다. (중략)

• Journal of Korean Society of Environmental Engineers
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• v.35 no.4
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• pp.294-300
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• 2013

In this study, major parameter of partial nitritation was investigated for the stable operation. In order to establish partial nitritation system, prevailing parameters such as temperature, BA (bicarbonate alkalinity) and pH were evaluated. As a result, it is inferred that appropriate bicarbonate alkalinity ratio (mg $NaHCO_3{\cdot}L^{-1}/mg$ Inf. $NH_4{^+}-N{\cdot}L^{-1}$) drives stable 50% partial nitritation at $32^{\circ}C$ and ambient temperature, respectively. Alkalinity ratio was proposed as new strategy for 50% partial nitritation without pH control in both temperature regimes. Because of the results, it was added amound of BA required only for 50% nitritation to inhibit nitratation. The effluent $NO_2{^-}-N/NH_4{^+}-N$ ratio reached almost 100% when initial bicarbonate alkalinity ratios (mg $NaHCO_3{\cdot}L^{-1}/mg$ Inf. $NH_4{^+}-N{\cdot}L^{-1}$) were 6.8 (R1) and 6.7 (R2), respectively. Polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) results demonstrated that AOB was the dominant nitrifying bacteria and NOB was negligible after adopting process control.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.10
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• pp.1789-1797
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• 2000

The objective of this study was to assess parameters affecting nitrite accumulation, which offers advantages in terms of less aeration energy and carbon consumption for denitrification. The influence of the alkalinity to $NH_4{^+}-N$ concentration ratio, pH, FA(free ammonia) concentration and temperature on nitrite accumulation was investigated. The experiment was performed with supernatant from dewatering process of anaerobic digested sludge using a submerged biofilm reactor. The influent contains high strength of ammonium nitrogen and the alkalinity was insufficient for complete nitrification. An increased nitrite accumulation was observed with increase in alkalinity to $NH_4{^+}-N$ concentration ratio. The increase in alkalinity to $NH_4{^+}-N$ concentration ratio has been a maior reason for the high pH value and FA concentration in the reactor. It can be considered that selective inhibition of Nitrobacter can be causes of nitrite accumulation. The nitrite accumulation increased with increment of temperature at fixed alkalinity to $NH_4{^+}-N$ concentration ratio.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.323-329
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• 2005

In this paper, performance of a hybrid sequential aerobic-anaerobic natural system was investigated. Continuous aerobic and anoxic conditions were created by alternatively placing waste stabilization pond (WSP) and wale. hyacinth pond (WHP). Two pilot-scale treatment lines were built and operated; The first consists of WSP integrated with WHP and the second of WSP connected with Dark Pond(DP), namely control system ponds which were used to examine the effects of water hyacinth on nitrification and de-nitrification. The overall performance in nitrogen was 86% reduction in WSP-WHP and 36% in WSP-control pond system. Nitrogen was mostly removed by nitrification and de-nitrification which simultaneously occurred in the same water hyacinth ponds. For the de-nitrification, benthic layer was found out to be adequate support as a carbon source. In addition, WSP-WHP system was very effective in reducing phosphorus. Overall P removal efficiency in WSP-WHP is 81%, while it is only 16% in WSP-control. difference in phosphorus reduction between those two systems is thought to be caused by the plants and probably their roots producing extra-cellular materials, but these aspects need to be further studied.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.1
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• pp.73-80
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• 2010

Two nitrite oxidizing bacteria, NOB1 and NOB2, were isolated from anaerobic digester liquer of food wastewater and analyzed for their growth characteristics and the ability to oxidize nitrite under different temperature, pH, and DO( dissolved oxygen) concentrations. Both of the isolated strains have shown the best growth at pH 7.0 and at $35^{\circ}C$, and also shown higher growth rate with the increasing dissolved oxygen concentrations. As the factors to restrict the growth of these strains, parameters such as pH and DO were found to be effective ones, by increasing (up to 9.0) or decreasing pH (up to 5.0), or lowing DO below 1.0 ppm. Especially, the ability to oxidize nitrite in both strains was about 50% lower in below 1.0 ppm of DO than above of 1.0 ppm. NOB2 was found to be two times greater in both the growth rate and the nitrite-oxidizing ability than NOB1.

• Applied Chemistry for Engineering
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• v.5 no.6
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• pp.925-934
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• 1994

Nickel recovered from the spent oil-hydrogenation catalysts was used in hydrogenation catalyst preparation. The spent catalyst contains approximately 21.8% Ni, 0.7% Mg, and small quantities of Al, Fe, and Zn. Nickel recovery was obtained by inorganic acid digestion in the order of HCI>$NHO_3$>$H_2SO_4$. For $HNO_3$, 3hour extraction with 3N solution was satisfactory. In the PH range of 6.5~9.0, Ni recovery was higher, but metallic impurities were found to be coprecipitated. The PH in the range of 7.0~9.0 seems to be the optimum condition for separation to obtain acceptable Ni precipitates without the decrease of purity. The catalysts prepared with reclaimed nickel by wet reduction methods showed catalytic activities close to those prepared using reagent nickel in the oil hydrogenation reaction. The surface areas of the support do not seem to affect the catalytic activity.

• Ecology and Resilient Infrastructure
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• v.11 no.2
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• pp.23-34
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• 2024

Sediment, aquifer materials, surface water, and groundwater from brackish Songji lake affected by salinity of seawater, were collected and a pilot scale column experiment was conducted to simulate the nitrogen transport through the hyporheic zone. Upstream experiments of groundwater displayed that groundwater containing a small amount of salt percolated into aquifers and sediments, maintaining low dissolved oxygen concentrations. In addition, partial denitrification occurred in the aquifer due to salinity and low dissolved oxygen, resulting in the accumulation of NO₂^-. In sediments,nitrogenous compounds were reduced due to adsorption by long residence times or microbial-mediated oxidation/reduction reactions. Downstream experiments of surface water displayed that surface water from the brackish lake, containing high concentrations of dissolved oxygen and salts, infiltrated into the sediments and aquifer, supplying high dissolved oxygen concentrations. This resulted in biological nitrification in the sediments and aquifer, which reduced nitrogen-based pollutants despite the high salt concentration in the surface water. Whereas partial denitrification at low dissolved oxygen concentrations in the upwelling mixing zone was observed by salinity and accumulated NO₂^-, nitrification at high dissolved oxygen concentrations in the downwelling mixing zone was not significantly affected by salinity. These results confirm that salinity in the brackish water lake has some influence on the nitrogen behavior of the hyporheic mixing zone, although nitrogen behavior is a complex combination of factors such as DO, pH, substrate concentration, and organic matter concentration.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.9
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• pp.1035-1043
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• 2007

A leachate containing an elevated concentration of organic and inorganic compounds has the potential to contaminate adjacent soils and groundwater as well as downgradient areas of the watershed. Moreover high-strength ammonium concentrations in leachate can be toxic to aquatic ecological systems as well as consuming dissolved oxygen, due to ammonium oxidation, and thereby causing eutrophication of the watershed. In response to these concerns landfill stabilization and leachate treatment are required to reduce contaminant loading sand minimize effects on the environment. Compared with other treatment technologies, leachate recirculation technology is most effective for the pre-treatment of leachate and the acceleration of waste stabilization processes in a landfill. However, leachate recirculation that accelerates the decomposition of readily degradable organic matter might also be generating high-strength ammonium in the leachate. Since most landfill leachate having high concentrations of nitrogen also contain insufficient quantities of the organic carbon required for complete denitrification, we combined a shortcut biological nitrogen removal (SBNR) technology in order to solve the problem associated with the inability to denitrify the oxidized ammonium due to the lack of carbon sources. The accumulation of nitrite was successfully achieved at a 0.8 ratio of $NO_2^{-}-N/NO_x-N$ in an on-site reactor of the sequencing batch reactor (SBR) type that had operated for six hours in an aeration phase. The $NO_x$-N ratio in leachate produced following SBR treatment was reduced in the landfill and the denitrification mechanism is implied sulfur-based autotrophic denitrification and/or heterotrophic denitrification. The combined leachate recirculation with SBNR proved an effective technology for landfill stabilization and nitrogen removal in leachate.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.5
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• pp.228-235
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• 2016

Nitrite accumulation is essential for constructing an anammox process. As the pH in the reactor exerts a complicated and strong influence on the reaction rate, we investigated its effects upon treatment of an ammonic wastewater (2,000 mgN/L) through modeling and experiment. The modeling results indicated that the reaction stability is strongly affected by pH, which results in a severe reduction of the 'stable region' of operation under alkaline environments. On a coordinate of the total ammonia nitrogen (TAN) concentration vs. pH, the maximal stable reaction rates and the maximal nitrite accumulation potentials could be found on the 'stability ridge' that separates the stable region from the unstable region. We achieved a stable and high ammonia oxidation rate (${\sim}6kgN/m^3-d$) with a nitrite accumulation ratio of ~99% when operated near the 'stability ridge'. The optimum pH that can be observed in experiments varies with the TAN concentrations utilized, although the intrinsic optimum pH is fixed. The direction of change is that the optimum operational pH falls as the TAN concentration increases, which is in excellent accordance with the observations in the literature. The optimum operational pH for 95% nitritation was predicted to be ~8.0, whereas it was ~7.2 for 55% partial nitritation to produce an anammox feed in our experimental conditions.