• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.920-926
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• 2007

The upflow Biobead$^{(R)}$ process, one of biological aerated filters (BAF), which was used commercially, invented for removal of organic materials and nitrification. This process was modified to enhance the ability of denitrification through the induction of pre-anoxic tank. In this research, we investigated the effects of hydraulic retention time (HRT) and backwashing period in aerobic tank. The characteristics of nitrifying bacteria, which are composed of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), also investigated using fluorescence in situ hybridization (FISH). Even though the HRT was shortened, the efficiency of nitrification was not decreased when the organic loading rate and ammonium-nitrogen loading rate were $2.10kg/m^3/day$ and $0.25kg/m^3/day$, respectively. And then the distribution ratios of AOB and NOB showed the similar patterns. However, when the backwashing period was lengthened from 12 hours to 24 hours in aerobic 1 tank, the nitrification efficiency was decreased to 63.9% from 89.2%. The results of FISH explained that this decrease of nitrification efficiency was caused by the decrease of distribution ratio of AOB in aerobic 1 tank. The nitrification efficiencies of aerobic 1 and aerobic 2 tank were increased when the backwashing period was lengthened because of relative high distribution ratios of nitrifying bacteria.

• Korean Journal of Environmental Agriculture
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• v.31 no.2
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• pp.170-174
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• 2012

BACKGROUND: Inappropriate discharge of wastewaters and industrial effluents are becoming detrimental to the aquatic environment. The presence of toxic substances on wastewaters can be detected by physicochemical and biological methods. However, physicochemical methods do not give any information about biological toxicity. Therefore, in this study we tried to detect the presence of toxic substance on waters using sulfur-oxidizing bacteria (SOB) as a bioassay. MATERIALS AND RESULTS: The SOB biosensor was first stabilized using synthetic stream water and operated in both continuous and semi-continuous mode. When the SOB biosensor was operated in continuous mode, the effluent electrical conductivity (EC) stabilized at~1.72 dS/m. While in the case of semi-continuous, the EC stabilized at~0.6 dS/m. The SOB system was also operated at different reaction times to ascertain the shortest reaction time for monitoring the toxicity. Finally, the SOB biosensor was fed with nitrite as toxic substance. When 5 mg/L of nitrite was added to the SOB system, the EC decreased immediately. However, the EC recovered after few cycle. CONCLUSION: This study shows that the SOB biosensor can be used as warning system to protect aquatic environment from hazardous materials. Although SOB biosensor can not give specific information about the toxic substances, it can assess whether the water is toxic or not.

• Journal of Microbiology and Biotechnology
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• v.20 no.3
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• pp.485-493
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• 2010

A modified graphite felt electrode with neutral red (NR-electrode) was shown to catalyze the chemical oxidation of nitrite to nitrate under aerobic conditions. The electrochemically oxidized NR-electrode (EO-NR-electrode) and reduced NR-electrode (ER-NR-electrode) catalyzed the oxidation of $1,094{\pm}39$ mg/l and $382{\pm}45$ mg/l of nitrite, respectively, for 24 h. The electrically uncharged NR-electrode (EU-NR-electrode) catalyzed the oxidation of $345{\pm}47$ mg/l of nitrite for 24 h. The aerobic bacterial community immobilized in the EO-NR-electrode did not oxidize ammonium to nitrite; however, the aerobic bacterial community immobilized in the ER-NR-electrode bioelectrochemically oxidized $1,412{\pm}39$ mg/l of ammonium for 48 h. Meanwhile, the aerobic bacterial community immobilized on the EU-NR-electrode biochemically oxidized $449{\pm}22$ mg/l of ammonium for 48 h. In the continuous culture system, the aerobic bacterial community immobilized on the ER-NR-electrode bioelectrochemically oxidized a minimal $1,337{\pm}38$ mg/l to a maximal $1,480{\pm}38$ mg/l of ammonium to nitrate, and the community immobilized on the EU-NR-electrode biochemically oxidized a minimal $327{\pm}23$ mg/l to a maximal $412{\pm}26$ mg/l of ammonium to nitrate every two days. The bacterial communities cultivated in the ER-NR-electrode and EU-NR-electrode in the continuous culture system were analyzed by TGGE on the $20^{th}$ and $50^{th}$ days of incubation. Some ammonium-oxidizing bacteria were enriched on the ER-NR-electrode, but not on the EU-NR-electrode.

• Journal of Korean Society on Water Environment
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• v.34 no.1
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• pp.96-108
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• 2018

Large efforts have recently been made on research and development of sustainable and energy-efficient short-cut nitrogen removal processes owing to strong attention to the energy neutral/positive wastewater treatment system. Anaerobic ammonium oxidizing bacteria (anammox bacteria) have been highlighted since 1990's due to their unique advantages including 60% less energy consumption, nearly 100% reduction for carbon source requirement, and 80% less sludge production. Side-stream short-cut nitrogen removal using anammox bacteria and partial nitritation anammox (PN/A) has been well established, whereas substantial challenges remain to be addressed mainly due to undesired main-stream conditions for anammox bacteria. These include low temperature, low concentrations of ammonia, nitrite, free ammonia, free nitrous acid or a combination of those. In addition, an anammox side-stream nitrogen management is insufficient to reduce overall energy consumption for energy-neutral or energy positive water resource recovery facility (WRRF) and at the same time to comply with nitrogen discharge regulation. This implies the development of the successful main-stream anammox based technology will accelerate a conversion of current wastewater treatment plants to sustainable water and energy recovery facility. This study discusses the status of the research, key mechanisms & interactions of the protagonists in the main-stream PN/A, and control parameters and major challenges in process development.

• Journal of Microbiology and Biotechnology
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• v.28 no.7
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• pp.1168-1177
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• 2018

The aim of this study was to investigate the microbial community of three tannery wastewater treatment plants (WWTPs) involved in nitrification by Illumina MiSeq sequencing. The results showed that highly diverse communities were present in tannery wastewater. A total of six phyla, including Proteobacteria (37-41%), Bacteroidetes (6.04-16.80), Planctomycetes (3.65-16.55), Chloroflexi (2.51-11.48), Actinobacteria (1.91-9.21), and Acidobacteria (3.04-6.20), were identified as the main phyla, and Proteobacteria dominated in all the samples. Within Proteobacteria, Beta-proteobacteria was the most abundant class, with the sequence percentages ranging from 9.66% to 17.44%. Analysis of the community at the genus level suggested that Thauera, Gp4, Ignavibacterium, Phycisphaera, and Arenimonas were the core genera shared by at least two tannery WWTPs. A detailed analysis of the abundance of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) indicated that Nitrosospira, Nitrosomonas, and Nitrospira were the main AOB and NOB in tannery wastewater, respectively, which exhibited relatively high abundance in all samples. In addition, real-time quantitative PCR was conducted to validate the results by quantifying the abundance of the AOB and total bacteria, and similar results were obtained. Overall, the results presented in this study may provide new insights into our understanding of key microorganisms and the entire community of tannery wastewater and contribute to improving the nitrogen removal efficiency.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.2
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• pp.195-206
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• 2014

Immobilization of anaerobic ammonium oxidizing bacteria has been studied to enhance the biomass retention of the slowly growing bacteria and the process stability. The purpose of this study was to compare the nitrogen removal efficiency of granular and immobilized anammox bacteria with poly vinyl alcohol and alginate. The specific anammox activity of the granular, homoginized and immobilized anammox bacteria were $0.016{\pm}0.0002gN/gVSS/d$, $0.011{\pm}0.001gN/gVSS/d$ and $0.007{\pm}0.0005gN/gVSS/d$, respectively. Although the activity decreased to 43.7 % of the original one due to low pH and $O_2$ exposure during the homogination and the immobilization, it was rapidly recovered within 7 days in the following continuous culture. When synthetic T-N concentrations of 100, 200, 400, 800 mg/L were fed, the immobilized anammox bacteria showed higher nitrogen removal efficiencies at all operational conditions than those of granular anammox bacteria. When the sludge retention time was shorten below 30.7 days and the reject water was fed, the nitrite removal efficiency of the granular anammox bacteria dropped to 8 % of the initial value, while that of the immobilized anammox bacteria was maintained over 95 % of the initial one. The immobilization with poly vinyl alcohol and alginate would be a feasible method to improve the performance and stability of the anammox process.

• Journal of Microbiology and Biotechnology
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• v.18 no.11
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• pp.1826-1835
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• 2008

An autotrophic denitrification reactor (ADR-l) and a heterotrophic denitrification reactor (HDR-2) were operated to remove nitrate and nitrite in an anoxic environment in raw sewage. The $NO_3$-N removal rate of ADR-l was shown to range from 52.8% to 78.7%, which was higher than the $NO_3$-N removal rate of HDR-2. Specific denitrification rates (SDNR) of ADR-l and HDR-2 were 3.0 to 4.0 and 1.1 to $1.2\;mgNO_3$-N/gVSS/h, respectively. From results of restriction fragment length polymorphism (RFLP) of the 16S rRNA gene, Aquaspirillum metamorphum, Alcaligenes defragrans, and Azoarcus sp. were $\beta$-Proteobacteria that are affiliated with denitritying bacteria in the ADR-l. Specifically, Thiobacillus denitrificans was detected as an autotrophic denitrification bacteria. In HDR-2, the $\beta$-Proteobacteria such as Denitritying-Fe-oxidizing bacteria, Alcaligenes defragrans, Acidovorax sp., Azoarcus denitrificans, and Aquaspirillum metamorphum were the main bacteria related to denitrifying bacteria. The $\beta$-and $\alpha$-Proteobacteria were the important bacterial groups in ADR-l, whereas the $\beta$-Proteobacteria were the main bacterial group in HDR-2 based on results of fluorescent in situ hybridization (FISH). The number of Thiobacillus denitrificans increased in ADR-l during the operation period but not in HRD-2. Overall, the data presented here demonstrate that many heterotrophic denitritying bacteria coexisted with autotrophic denitrifying bacteria such as Thiobacillus denitrificans for nitrate removal in ADR-l. On the other hand, only heterotrophic denitritying bacteria were identified as dominant bacterial groups in HDR-2. Our research may provide a foundation for the complete nitrate removal in raw sewage of low-COD concentration under anoxic condition without any external organic carbon or the requirement of post-treatment.

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

• Korean Journal of Ecology and Environment
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• v.39 no.2 s.116
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• pp.219-225
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• 2006

Bacterial community structure in the Juam Reservoir was analysed using fluorescent in situ hybridization (FISH) technique from April 2005 to January 2006. Total bacterial numbers varied in the range of 1.58 ${\sim}\;2.73{\times}\;10^6\;cells\;mL^{-1}$ proportional to the concentration of chi-a and had the minimal value in January. The ratios of ${\alpha}\;{\cdot}\;{\beta}\;{\cdot}\;{\gamma}$-subclass proteobacteria and Cytophaga-Flavobacterium (CF) group to total bacteria ranged from 45.1% to 77.5%, and the ratios of ${\alpha}\;{\cdot}\;{\beta}\;{\cdot}\;{\gamma}$-subclasses to total bacteria in June and September with the concentration of chi-a measured were lower than those ratios in April and January. It suggests that enriched growth of Microcystis aeruginosa may inhibit the metabolic activlty of ${\alpha}\;{\cdot}\;{\beta}\;{\cdot}\;{\gamma}$-subclass proteobacteria. However, the ratio of CF group bacteria represented no large change depending on algal bloom. In terms of nitrifying bacteria, the numbers of ammonia-oxidizing bacteria ranged from 9.9 ${\times}\;10^4\;to\;25.5\;{\times}10^4\;cells\;mL^{-1}$ with sharp fluctuation whereas those of nitrite-oxidizing bacteria varied in 8.7${\sim}9.8{\times}10^4\;cells\;mL^{-1}$ without noticeable change except the maximal value of $20.3{\times}10^4\;cells\;mL^{-1}$ in January maybe due to the high DO.

• Membrane and Water Treatment
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• v.10 no.4
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• pp.265-275
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• 2019

This study aimed to develop a compact partial nitritation step by forming granules with high Ammonia-Oxidizing Bacteria (AOB) fraction using the Air-lift Granulation Reactor (AGR) and to evaluate the feasibility of treating reject water with high ammonium content by combination with the Anammox process. The partial nitritation using AGR was achieved at high nitrogen loading rate ($2.25{\pm}0.05kg\;N\;m-3\;d^{-1}$). The important factors for successful partial nitritation at high nitrogen loading rate were relatively high pH (7.5~8), resulting in high free ammonia concentration ($1{\sim}10mg\;FA\;L^{-1}$) and highly enriched AOB granules accounting for 25% of the total bacteria population in the reactor. After the establishment of stable partial nitritation, an effluent $NO_2{^-}-N/NH_4{^+}-N$ ratio of $1.2{\pm}0.05$ was achieved, which was then fed into the Anammox reactor. A high nitrogen removal rate of $2.0k\; N\;m^{-3}\;d^{-1}$ was successfully achieved in the Anammox reactor. By controlling the nitrogen loading rate at the partial nitritation using AGR, the influent concentration ratio ($NO_2{^-}-N/NH_4{^+}-N=1.2{\pm}0.05$) required for the Anammox was controlled, thereby minimizing the inhibition effect of residual nitrite.