• 한국환경농학회:학술대회논문집
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• 2011.07a
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• pp.296-296
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• 2011

• Journal of Environmental Science International
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• v.21 no.8
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• pp.989-996
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• 2012

Nitrate contamination of water environments can create serious problems such as eutrophication of rivers. Conventional biological processes for nitrate removal by heterotrophic denitrification often need additional organic substrates as carbon sources and electron donors. We tried to accelerate biological denitrification by using bioelectrochemical reactor (BER) in which electrode works as an electron donor. Denitrification activity of 8 environmental samples from various sediments, soils, groundwaters, and sludges were tested to establish an efficient enrichment culture for BER. The established enrichment culture from a soil sample showed stable denitrification activity without any nitrite accumulation. Microbial community analysis by using PCR-DGGE method revealed that dominant denitrifiers in the enrichment culture were Pantoea sp., Cronobacter sakazakii, and Castellaniella defragrans. Denitrification rate ($0.08kg/m^3{\cdot}day$) of the enrichment culture in BER with electrode poised at -0.5 V (vs Ag/AgCl) was higher than that ($2.1{\times}10^{-2}kg/m^3{\cdot}day$) of BER without any poised potential. This results suggested that biological denitrification would be improved by supplying potential throughout electrode in BER. Further research using BER without any organic substrate addition is needed to apply this system for bioremediation of water and wastewater contaminated by nitrate.

• Journal of Soil and Groundwater Environment
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• v.27 no.3
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• pp.41-49
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• 2022

This study utilized citric acid as a floating agent in biological denitrification process and assessed its role under different carbon supplying conditions. Several microcosm tests including citric acid active (CAA), precipitating tablet release active (PTRA) and floating tablet release active (FTRA) were conducted to evaluate nitrate denitrification efficacy. In CAA reactors, nitrate removal was accompanied by the formation of denitrification by-products such as nitrite and nitrous oxide, with the extent of nitrate removal being proportional to citric acid concentration. These results suggest that citric acid induced heterotrophic biological denitrification. PTRA reactor that incorporated CAA and the same electron donor showed a similar denitrification efficiency to CAA reactor. FTRA reactor, which contained the same amount of fumarate as PTRA, enhanced denitrification by 7% as compared to the PTRA reactor. The overall results of this work indicate that surplus citric acid can be efficiently utilized in heterotrophic denitrification.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.5
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• pp.622-629
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• 2014

This study induced biological denitrification and nitrification via a biofiltration process with the view of removing nitrogen from land-based fish farm effluent. To achieve this, we operated an aquaculture nitrogen-removal system that includes a denitrification and nitrification reactor [working volume 40 L, flow rate 64.8 L, HRT (hydraulic retention time) 14.8 h, HRT considering recycling of NOx 7.4 h]. In the continuous process, the nitrification rate of ammonium nitrogen exceeded 90% at a steady state and the denitrification efficiency exceeded 80% with recycling to a pre-anoxic reactor. In addition, the pH in the final effluent was lower with a low influent water alkalinity averaging 100 mg/L (as $CaCO_3$). For effective denitrification reactions, carbon must be supplied via particulate organic matter (POM) hydrolysis because of the low C/N (carbon/nitrogen) ratio in the water.

• Journal of Microbiology and Biotechnology
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• v.16 no.5
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• pp.678-682
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• 2006

To remove nitrate from wastewater, a novel bioelectrochemical denitrification system is introduced. In this proposed system, biological reactions are coupled with reactions on the electrode, whereby the electrons are transferred to the bacterial enzymes via a mediator as an electron carrier. The denitrification reaction was achieved with permeabilized Ochrobactrum anthropi SY509 containing denitrifying enzymes, such as nitrate reductase, nitrite reductase, and nitrous oxide reductase, and methyl viologen was used as the mediator. The electron transfer from the electrode to the enzymes in the bacterial cells was confirmed using cyclic voltammetry. A high removal efficiency of nitrate was achieved when the bioelectrochemical system was used with the permeabilized cells. Furthermore, when the permeabilized cells were immobilized to a graphite felt electrode using a calcium alginate matrix containing graphite powder, a high removal efficiency was achieved (4.38 nmol/min mg cell) that was comparable to the result when using the free permeabilized cells.

• Journal of Soil and Groundwater Environment
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• v.25 no.2_spc
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• pp.16-27
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• 2020

Nitrate contamination has received much attention at local as well as regional scales. The domestic situation is not out of exception, and it has been reported to be very serious, particularly within agricultural areas as a result of excessive usage of nitrogen fertilizers. Meanwhile, nitrate can be naturally attenuated by denitrification in subsurface environments. The denitrification occurs through biotic (biological) and abiotic processes, and numerous previous studies preferentially focused the former. However, abiotic denitrification seems to be significant in specific environments. For this reason, this study reviewed the previous studies that focused on abiotic denitrification processes. Firstly, the current status of nitrate contamination in global and domestic scales is presented, and then the effect of geological media on denitrification is discussed while emphasizing the significance of abiotic processes. Finally, the implications of the literature review are presented, along with future research directions that warrant further investigations. The results of previous studies demonstrated that several geological agents could play a vital role in reducing nitrate. Iron-containing minerals such as pyrite, green rust, magnetite, and dissolved ferrous ion are known to be powerful electron donors triggering denitrification. In particular, it was proven that the rate of denitrification by green rust was comparative to that of biological denitrification. The results indicate that abiotic denitrification should be taken into account for more accurate evaluation of denitrification in subsurface environments.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.4
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• pp.446-454
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• 2005

An economic treatment method to remove oxidized nitrogen from wastewater is biological denitrification with organic matters. Several organics can be used, however, methanol is commonly used. When methanol is provided, M:N (Methanol to Nitrogen) ratio is used to define methanol demand for denitrification. In this study, two artificial wastewaters were provided to a biological system to evaluate denitrification performance. Differences of influent total CODcr from effluent soluble CODcr were converted to methanol equivalent and oxidized nitrogen difference between influent and effluent were converted to nitrate equivalent to define M:N ratios. Modes I, II, III, I-1 and IV showed 5.1, 2.7, 3.3, 2.3 and 2.6 of M:N ratios, respectively. Since denitrifying microorganisms had to build a new metabolic system for methanol and influent organics, initial operation mode, Mode I, required more methanol and this resulted in high M:N ratios compared with later operation mode, Mode I-1. Salt in influent did not show inhibitory effects on denitrfication, although this was believed to increase effluent SS and soluble CODcr concentrations in Mode III, I-1 and IV, respectively. The concentrations of effluent soluble $COD_{Mn}$ did not changed much with influent salt.

• KSBB Journal
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• v.23 no.6
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• pp.535-540
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• 2008

In this study, the effects of several factors such as initial nitrate concentration, C/N ratio, biomass amount and external carbon source on denitrification process were investigated using synthetic wastewater and sludge obtained from wastewater treatment facility. As a result, the condition of lower initial nitrate concentration was increased to the removal rate of nitrate than that of high concentration. The increases of C/N ratio and initial biomass amount were linearly enhanced the removal rate. The use of ethanol as external carbon source was shown the highest removal yield than that of others.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.222-229
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• 2006

The treatment performance and operational parameters of a tertiary wastewater treatment process a biological filtration system were investigated. The biological filtration system consisted of a nitrification filter (Fiter 1) and a polishing filter with anoxic and aerobic parts (Filter 2). SS, T-C-BOD, and T-N in effluent were kept stable at less than 3, 5 mg/L, and 5 mgN/L, respectively, under a HRT in Filter (filter-bed) of 0.37~2.3 h. T-N at the outlet of Filter 2 were about 1~5 mgN/L under the condition of LV of 50~202 m/d. In Filter 2, denitrification was accomplished under LV of 50~168 m/d in a 1 m filter-bed. However, the denitrification capacity reached the maximum when the linear velocity was increased to 202 m/d. Relationship between increase in microorganism and headloss was clearer in Filter 2. As a result, the denitrification rate increased from 1.0~2.3 kgN/($m^3-filter-bed{\cdot}d$) as the headloss increased. The COD removal rate was 6.0~9.6 kgCOD/($m^3-filter-bed{\cdot}d$) when operated with Filters 1 and 2. These results mean that captured bacteria contributed a part of COD consumption and denitrification. The maximum nitrification and denitrification rate was 0.5 and 4 kgN/($m^3-filter-bed{\cdot}d$) in Filter 1 and 2.The ratio of backwashing water to the treated water was about 5~10 %. In Filter 1, wasted sludge in backwashing was only 0.7~5.3 gSS/($m^3$-treated water). In Filter 2, added methanol was converted into sludge and its value was 8.0~24 gSS/($m^3$-treated water). These results proved that this process is both convenient to install as tertiary treatment and cost effective to build and operate.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1124-1129
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• 2008

Cokes wastewater is one of the most toxic industrial effluents since it contains high concentrations of pollutants, such as phenol, ammonia, thiocyanate and cyanides. Although biological pre-denitrification process has been used to treat this wastewater in Korea, unexpected failure in nitrogen removal occasionally occurs during summer season. In this study, therefore, we examined inhibitory effects of phenol, ammonia, thiocyanate, ferric cyanide and free cyanide on biological denitrification according to temperature variation ($20{\sim}38^{\circ}C$). Batch experiments showed that denitrification rate was faster in summer ($38^{\circ}C$) than other seasons, and removal rates of pollutants increased with increasing temperature. Phenol, ammonia, thiocyanate and ferric cyanide did not inhibit denitrification even at its high concentration (200 mg/L). However free cyanide above 0.5 mg/L seriously inhibited the bilolgical denitrification reaction. Inhibitory effect of these pollutants was reduced with increasing temperature.