• Korean Journal of Agricultural and Forest Meteorology
• /
• v.1 no.2
• /
• pp.160-164
• /
• 1999

Subsurface environments, including the intermediate vadose zone and aquifers, may be contributing to increased atmospheric concentrations of $N_2$O. Denitrification appears to be the major source of $N_2$O in the subsurface environment. In the intermediate vadose zone, the level of denitrifying activity is dependent on the soil morphology, particularly stratified layers within the soil profile, which impede water and solute movement and create conditions favorable for denitrification. Movement of organic C from the soil surface appears to support denitrifying activity by providing an energy source and increasing the consumption of $O_2$. Denitrirication and $N_2$O production have been observed in aquifers but appear to be of greatest significance in shallow unconfined aquifers. The lack of organic C, N $O_2$, or anaerobiosis is often a limiting factor for activity but seems to be site specific. The presence of denitrifying bacteria does not appear to be a major limitation, based on published results, but the ubiquity of denitrifiers in subsurface environments needs to be confirmed. The fate of the $N_2$O produced in subsurface environments is unknown. Transport of $N_2$O by up ward diffusion, by outgassing at contacts with surface waters, and by ground water use need to be quantified to determine the contribution to atmospheric $N_2$O. Contamination of subsurface environment with N $O_3$$^{ }$ and organics has the potential for increasing the contribution to atmospheric $N_2$O by enhancing denitrification .

• Korean Journal of Soil Science and Fertilizer
• /
• v.21 no.2
• /
• pp.149-159
• /
• 1988

This study was made to investigate the effect of pesticides on microflora to nitrogen metabolism, nitrification and nitrogen fixing activity in the submerged soil. The results are summarized as follows; Pesticides treatment leaded to the inhibition of $NH_4{^-}$-oxdizers, $NO_3{^-}$-reducer, and denitrifying bacteria population. $NO_2{^-}$-oxdizers were inhibited by cabamate compounds, carbofuran and MIPC. Simetryne seemed to stimulate the denitrifying bacteria at 60 days after incubation. Generally, formation of $NO_2{^-}$ and $NO_3{^-}$ tended to decrease by pesticides application. Pesticides application stimulated Azotobacter and Clostridia populations, while simetryne inhibited Athiorhodaceae and Thiorhodaceae. However acephate seemed to be stimulatory to blue-geen algae. $C_2H_2$-reducing activity by acephate was clearly appeared. The change of $C_2H_2$-reducing activity did not seems to be affected by pesticides application.

• Microbiology and Biotechnology Letters
• /
• v.40 no.1
• /
• pp.30-38
• /
• 2012

We investigated the effects on soil microbial diversity and the growth promotion of red pepper resulting from inoculation with a microbial agent composed of Bacillus subtilis AH18, B. licheniformis K11 and Pseudomonas fluorescens 2112 in a red pepper farming field. Photosynthetic bacteria, Trichoderma spp., Azotobacter spp., Actinomycetes, nitrate oxidizing bacteria, nitrite oxidizing bacteria, nitrogen fixing bacteria, denitrifying bacteria, phosphate solubilizing bacteria, cellulase producing bacteria, and urease producing bacteria are all indicator microbes of healthy soil microbial diversity. The microbial diversity of the consortium microbial agent treated soil was seen to be 1.1 to 14 times greater than soils where other commercial agent treatments were used, the latter being the commercial agent AC-1, and chemical fertilizer. The yield of red pepper in the field with the treated consortium microbial agent was increased by more than 15% when compared to the other treatments. Overall, the microbial diversity of the red pepper farming field soil was improved by the consortium microbial agent, and the promotion of growth and subsequent yield of red pepper was higher than soils where the other treatments were utilized.

• Journal of Korean Society on Water Environment
• /
• v.20 no.5
• /
• pp.480-487
• /
• 2004

This study was conducted to find the effect of electron acceptors on the formation of granular sludge by using four different types of electron acceptors. The phosphorous uptake, denitrification, and sulfate reduction in anoxic modes were simultaneously occured because of the presence of the polyphosphate accumultating organism(PAO) that utilize nitrate and sulfate as an electron acceptor in the anoxic zone. Denitrirying phosphorous removal bacteria(DPB) was enriched under anaerobic/anoxic/aerobic condition with a nitrate as an electron acceptor, and desulfating phosphorous removal bacteria(DSPB) was enriched under anaerobic/anoxic/aerobic condition with a sulfate as an electron acceptor. Polyphosphate accumulating organism(PAO) were enriched in the anaerobic/aerobic SBR. PAO took up acetate faster than DPB and DSPB during the aerobic phase. The sludge with nitrate and sulfate as an electron acceptors grew as a granules which possessed high activity and good settleability. In the anaerobic/aerobic modes, typical floccular growth was observed. In the result of bench-scale experiment, simultaneous reactions of phosphorus uptake, denitrification and sulfate reduction were observed under anoxic condition with nitrate and sulfate as an electron acceptors. These results demonstrated that the anaerobic/anoxic modes with nitrate and sulfate as an electron acceptors played an important role in the formation of the sludge granulation.

• Journal of Korean Society of Forest Science
• /
• v.86 no.1
• /
• pp.98-104
• /
• 1997

Soil pollution intensity at Mt. Namsan in Seoul city which was expected to show significant soil contamination due to long-term air pollution was evaluated by comparing soil chemical properties at Mt. Kyebangsan in Hongcheon area as a control, and the bacteria participating in nitrogen or sulfur mineralization were assayed simultaneously in order to evaluate the validity of N and/or S mineralization bacteria as an index of soil contamination. The soil of Mt. Namsan showed 10 times higher concentration of hydrogen ion compared to that of Mt. Kyebangsan, which indicated that the soil had relatively been acidified seriously. Especially, large amount of canons were thought to be leached out from the soil, while the amount of extractable Al was getting larger and larger, which result in serious problems in soil ecosystem of the mountain. I could infer from soil chemical properties of the four study sites that the major reason of soil acidification was SOx deposition. However, the sulfur-reducing bacteria were not significantly different between the two regions, which indicated that the microbial dynamics of the soil ecosystem was not controlled by simple factor, but by multiple factors. By the way, the dynamics of bacteria participating in denitrification process was different between the two regions, which was more active at Mt. Kyebangsan than at Mt. Namsan. Thus, the microbial assay for nitrogen mineralization is desirable to be examined as a tool for evaluating soil health or microbial activity in soil ecosystem.

• Korean Journal of Soil Science and Fertilizer
• /
• v.39 no.6
• /
• pp.409-414
• /
• 2006

Sulfur-oxidizing bacteria were enumerated and isolated from a steady-state anaerobic master culture reactor (MCR) operated for over six months under a semi-continuous mode and nitrate-limiting conditions using thiosulfate as an electron donor. Most are Gram-negative bacteria, which have sizes up to 12 m. Strains AD1 and AD2 were isolated from the plate count agar (PCA), and strains BD1 and BD2 from the solid thiosulfate/nitrate medium. Based on the morphological, physiological, FAME and 16S rDNA sequence analyses, the two dominant strains, AD1 and AD2, were identified as Paracoccus denitrificans and Paracoccus versutus (formerly Thiobacillus versutus), respectively. From the physiological results, glucose was assimilated by both strains AD1 and AD2. Heterotrophic growth of strains AD1 and AD2 could be a more efficient way of obtaining a greater amount of biomass for use as an inoculum. Even though facultative autotrophic bacteria grow under heterotrophic conditions, autotrophic denitrification would not be reduced.

• 한국생물공학회:학술대회논문집
• /
• 2003.04a
• /
• pp.378-381
• /
• 2003

The characteristics of bio-beads made of various supports, in which denitrifying bacteria were entrapped after those cells were isolated from sludge in wastewater treatment plants, were studied in order to develop a novel BNR system. Four species were isolated, and the bead made of 12% PVA showed the highest denitrification rate. The best concentration of cell loading was 200 mg/ml, and there was no significant difference in performance by bead sizes. The bead reached the maximum denitrification rate after 4 batch experiments, and with cell leaking of $10^3$ CFU/ml its capacity retained until 25 batches.

• Journal of Microbiology and Biotechnology
• /
• v.15 no.3
• /
• pp.455-460
• /
• 2005

A pilot-scale sulfur particle autotrophic denitrification (SPAD) process for the treatment of municipal wastewater was operated for 10 months at Shihwa, Korea, and higher than $90\%\;NO^{-}_{3}-N$ removal efficiency was observed. Plate counting showed that the lower part of the denitrifying column reactor had the most autotrophic denitrifiers. The biofilm thickness formed on sulfur particles from the SPAD reactor was approximately $25-30\;{\mu}m$, measured by DAPI (4,6-diamidino-2-phenylindole) staining. The presence of bacteria inside the highly porous sulfur particle was also monitored by SEM observation of the internal surfaces of broken sulfur particles. Biofilm extracellular polymeric substances (EPS) analysis showed that the ratio of carbohydrate to protein decreased with the reactor heights at which biofilm-formed sulfur particles were obtained.

• Journal of Microbiology and Biotechnology
• /
• v.15 no.6
• /
• pp.1221-1228
• /
• 2005

Carbon electrode was applied to a wastewater treatment system as biofilm media. The spatial distribution of heterotrophic bacteria in aerobic wastewater biofilm grown on carbon electrode was investigated by scanning electron microscopy, atomic force microscopy, and biomass measurement. Five volts of electric oxidation and reduction potential were charged to the carbon anode and cathode of the bioelectrochemical system, respectively, but were not charged to electrodes of a conventional system. To correlate the biofilm architecture of bacterial populations with their activity, the bacterial treatment efficiency of organic carbons was measured in the bioelectrochemical system and compared with that in the conventional system. In the SEM image, the biofilm on the anodic medium of the bioelectrochemical system looked intact and active; however, that on the carbon medium of the conventional system appeared to be shrinking or damaging. In the AFM image, the thickness of biofilm formed on the carbon medium was about two times of those on the anodic medium. The bacterial treatment efficiency of organic carbons in the bioelectrochemical system was about 1.5 times higher than that in the conventional system. Some denitrifying bacteria can metabolically oxidize $H_{2}$, coupled to reduction of $NO_{3}^{-}\;to\;N_{2}$. $H_{2}$ was produced from the cathode in the bioelectrochemical system by electrolysis of water but was not so in the conventional system. The denitrification efficiency was less than $22\%$ in the conventional system and more than $77\%$ in the bioelectrochemical system. From these results, we found that the electrochemical coupling reactions between aerobic and anaerobic reactors may be a useful tool for improvement of wastewater treatment and denitrification efficiency, without special manipulations such as bacterial growth condition control, C/N ratio (the ratio of carbon to nitrogen) control, MLSS returning, or biofilm refreshing.

• Environmental Engineering Research
• /
• v.10 no.5
• /
• pp.227-238
• /
• 2005

The characteristics of nitrogen removal by the free cell and the immobilized cell of R. capsulatus were investigated. Denitrification by R. capsulatus cells resulted in reduction of ORP with the rapid depletion of DO and the increase of pH. Without accumulation of nitrite, the removal efficiencies of ${NO_3}^-$-N for the free cell and the immobilized cell were 99.1 and 99.3%, respectively. During the three-month experiment of goldfish breeding equipped with a water-purification biofilter, the average values of pH and total cell numbers present in an aquarium were not significantly different between water-purification system and the control. The average concentrations of ${NH_4}^+$-N and ${PO_4}^{2-}$-P in water-purification system were relatively low, compared to that in the control. Goldfish died at $11^{th}$, $16^{th}$, $43^{rd}$, and $67^{th}$ days in the control, while goldfish died at $10^{th}$, $20^{th}$, and $39^{th}$ days in the water-purification system. On the days of goldfish's death, the total concentrations of nitrogenous compounds except for ${NO_2}^--N$ were higher than those on the other days of the experiment, especially with the concentrations of ${NH_4}^+$-N ranging from 7.4 to 13.5 mg/L. The water-purification system also showed the less turbidity of water with more active movement of goldfish than the control. PVA gel beads showed almost the full denitrifying ability even after the long-term experiment. As a result, the water-purification system was effective to remove nitrogenous compounds with better survival of goldfish.