• Journal of Microbiology and Biotechnology
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• v.25 no.5
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• pp.569-578
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• 2015

Cold water paddy field soils are relatively unproductive, but can be ameliorated by supplementing with inorganic fertilizer from animal waste-based composts. The yield of two rice cultivars was significantly raised by providing either chicken manure or cow dung-based compost. The application of these composts raised the soil pH as well as both the total nitrogen and ammonium nitrogen content, which improved the soil's fertility and raised its nitrification potential. The composts had a measurable effect on the abundance of nitrogencycling-related soil microbes, as measured by estimating the copy number of various bacterial and archaeal genes using quantitative real-time PCR. The abundance of ammonia oxidizing archaea and bacteria was markedly encouraged by the application of chicken manure-based compost. Supplementation with the composts helped promote the availability of soil nitrogen in the cold water paddy field, thereby improving the soil's productivity and increasing the yield of the rice crop.

• Journal of Korean Society on Water Environment
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• v.23 no.3
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• pp.397-402
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• 2007

Anammox reactor seeded with sewage sludge from RBC reactor and anaerobic granule from full-scale UASB reactor treating distillery wastewater was operated. Mixed granule and suspended sludge in the ammonium oxidizing process were taken and analyzed to investigate microbial community structure by molecular methods such as gene cloning and phylogenetic tree analysis after 250 days of continuous cultivation. The average nitrogen removal rate showed $0.9kg\;N/m^3-day$ after 250 days of continuous operation, then the maximum nitrogen removal rate showd $1.9kg\;N/m^3-day$ when $2.1kg\;N/m^3-day$ of nitrogen loading rate was applied. As results of gene cloning and phylogenetic tree analysis, Three kinds of phylum were found to be Proteobacteria, Acidobacteria and Planctomycetes (anammox bacteria) in mixed granule. Five kinds of phylum were found to be Proteobacteria, Chlorobi, Planctomycetes, Nitrospirae and Verrucomicrobia in suspended sludge. We found planctomycete KSU-1 and putative new anammox bacteria in the reactor. Microbial structure represented different consortia depending on the types of sludge in the anammox reactor.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.10
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• pp.774-781
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• 2011

Nitric acid and hydrofluoric acid are used for acid pickling in zirconium alloy tubing manufacturing process. Nitrate and fluoride in the wastewater were treated by chemical coagulation and SOD (Sulfur Oxidation Denitrification) process. This study is investigated the effect of fluoride concentration and the optimal condition for SOD process. The limited fluoride concentration for SOD process was below 20 mg F-/L. The adjusted pH and alkalinity by NaOH and $NaHCO_3$ was shown to be more effective for removal of nitrate compared with using NaOH. Furthermore, the microbial activator mixed trace elements and ingredient for alkalinity did not only supplement with alkalinity but also enhance the growth and proliferation for sulfur-oxidizing bacteria. As a result, the inorganic industrial wastewater was successfully treated by the microbial activator in SOD process without continuous addition of seed sludge. Finally, SOD process was shown to remove nitrate in industrial wastewater and to contribute the microbial activator for activation of sulfur-oxidizing bacteria.

• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.319-324
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• 2016

In this study, pitch-based carbon fibers in the acid were radiated with an electron beam to modify their surface, and surface changes were investigated according to each treatment conditions. Nitric acid and hydrogen peroxide were used as a drenched acidic solution and an electron beam dose was set to 200 and 400 kGy. The use of nitric acid introduced more oxygen functional groups on carbon fiber surfaces than that of using hydrogen peroxide, and also introduced nitrogen functional groups into the carbon fiber surface. In addition, oxygen functional groups introduced on carbon fiber surface increased as the electron beam dose increased due to the fact that the oxidizing material can be easily formed by e-beam radiation in nitric acid than the hydrogen peroxide, and also the higher energy electron beam dose can help forming more oxidizing materials. Moreover, the generation of C=O functional groups was favorable when using nitric acid because oxidizing C-OH functional groups to the C=O functional groups mainly occurred by $NO_2$ radicals generated by the electron beam radiation in a nitric acid solution.

• Korean Journal of Microbiology
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• v.45 no.2
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• pp.112-118
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• 2009

Ammonia-oxidizing bacteria (AOB) are chemolithoautotrophs that play a key role in nitrogen removal from advanced wastewater treatment processes. Various AOB species inhabit and their community compositions vary over time in the wastewater treatment bioreactors. In this study, a hypothesis that operational and environmental conditions affect both the community compositions and the diversity of AOB in the bioreactors was proposed. To verify the hypothesis, the clone libraries based on ammonia monooxygenase subunit A were constructed using activated sludge samples from aerobic bioreactors at the Pohang, the Palo Alto, the Nine Springs, and the Marshall wastewater treatment plants (WWTPs). In those bioreactors, AOB within the Nitrosomonas europaea, N. oligotropha, N.-like, and Nitrosospira lineages were commonly found, while AOB within the N. communis, N. marina, and N. cryotolerans lineages were rarely detected in the samples. The AOB community structures were different in the bioreactors: AOB within the N. oligotropha lineage were the major microorganisms in the Pohang, the Palo Alto, and the Marshall WWTPs, while AOB within the N. europaea lineage were dominant in the Nine Springs WWTP. The correlations between the AOB community compositions of the wastewater treatment bioreactors and their operational (HRT, SRT, and MLSS) and environmental conditions (temperature, pH, COD, $NH_3$, and $NO_3{^-}$) were evaluated using a multivariate statistical analysis called the Redundancy Analysis (RDA). As a result, COD and $NO_3{^-}$ concentrations in the bioreactors were the statistically significant variables influencing the AOB community structures in the wastewater treatment bioreactors.

• Korean Journal of Microbiology
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• v.50 no.2
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• pp.164-168
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• 2014

The ecosystem of the Arctic region has been increasingly affected by global warming. Archaeal ammonia monooxygenase alpha subunit coding gene (amoA) which is a key enzyme for nitrification was used to investigate the effect of runoff water of ice melt on microbial community of nitrogen cycle. The archaeal amoA genes at coastal area of Svalbard, Arctic region were PCR-amplified and sequenced after clone library construction. Analysis of archaeal amoA gene clone libraries suggested that the station 188 which is in the vicinity to the area of runoff water harbor lower ammonia-oxidizing archaeal diversity than the station 176 and 184. The average amino acid sequence identity within all archaeal amoA gene clones was 94% (with 91% nucleotide sequence identity). While all the clones of the station 188 were affiliated with Nitrosoarchaeaum clade containing strains isolated from low-salinity and terrestrial environments, about 45% of total clones of the station 176 and 184 were related to marine Nitosopumilus clade. Interestingly, other typical archaeal amoA gene clones of thaumarchaeal I.1b clade frequently retrieved from terrestrial environments was identified at station 188. Microbial community of nitrogen cycle in marine sediment might be affected by input of sediments caused by runoff glacier melt waters.

• Microbiology and Biotechnology Letters
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• v.34 no.3
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• pp.257-264
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• 2006

An aerobic submerged membrane bioreactor (MBR) treating ammonium wastewater was studied in respect of nitrification characteristics and distribution of nitrification bacteria over a period of 350 days. MBR was fed with ammonium concentration of 500-1000 mg $NH_4-N/L$ at a nitrogen load of $1-2kg\;N/m^3{\cdot}d$. Overall ammonium oxidation rate increased with dissolved oxygen (DO) concentration, temperature, and sludge retention time (SRT). Under a higher concentration of free ammonia ($NH_3-N$) due to the decrease of ammonium oxidation rate, the nitrite ratio ($NO_2-N/NO_x-N$) in the effluent increased. The sudden collapse of nitrification efficiency accompanied by sludge foaming and the increase of sludge volume index (SVI) was observed unexpectedly during the operation. At the later stage of operation, additional carbon source was fed to the MBR and resulted in twice higher value of SVI and the decrease of ammonium oxidation rate. In fluorescence in situ hybridization (FISH) analysis, genus Nitrosomonas which is specifically hybridized with probe NSM156 was initially the dominant ammonia oxidizing bacteria and the amount of Nitrosospira gradually increased. Nitrospira was the dominant nitrite oxidizing bacteria during whole operational period. Significant amount of Nitrobacter was also detected which might due to the high concentration of nitrite maintained in the reactor.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.6
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• pp.332-339
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• 2015

Nitrogen removal is one of the most important issues about wastewater treatment because nitrogen is a primary pollutant caused various problems such as eutrophication. We developed a CANON microbial community by using AOB and ANAMMOX bacteria as seeding sources. When 100 mg-N/L of influent ammonium was supplied, the DO above 0.4 mg/L showed a very low TN removal efficiency while the DO of 0.3 mg/L showed TN removal efficiency as high as 71.3%. When the influent ammonium concentration was reduced to 50 mg/L, TN removal efficiency drastically deceased. However, TN removal efficiency was recovered to above 70% after 14 day operation when the influent nitrogen concentration was changed again from 50 mg-N/L to 100 mg-N/L. According to the operating temperature from $37{\pm}1^{\circ}C$ to $20{\pm}1^{\circ}C$, TN removal efficiency also rapidly decreased but gradually increased again up to $70.0{\pm}2.6$%. The analysis of PCR-DGGE showed no substantial difference in microbial community structures under different operational conditions. This suggests that if CANON sludge is once successfully developed from a mixture of AOB and ANAMMOX bacteria, the microbial community can be stably maintained regardless of the changes in operational conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.271-274
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• 2000

Gas sensor materials capable of detecting hydrogen gases (H$_2$) or nitrogen oxides (NO$\_$x/, primarily NO and NO$_2$) with high sensitivity have attracted much interest in conjunction with the growing concern to the protection of global environments. Beside conventional sensor materials, such as semiconductors., conducting polymers and solid electrolytes, the potential of sensor materials with a new method for detecting hydrogen gases or nitrogen oxides gas has also been tested. The breakdown voltage of porous varistors shifted to a low electric field upon exposure to H$_2$ gas, whereas it shifted to a reverse direction in an atmosphere containing oxidizing gases such as O$_3$ and NO$_2$ in the temperature range of 300 to 600$^{\circ}C$. Furthermore, it was found that the magnitude of the breakdown voltage shift, i. e. the magnitude of sensitivity, was well correlated with gas concentration, and that the H$_2$ sensitivity was improved by controlling the composition of the Bi$_2$O$_3$ rich grain boundary phase. However, NO$\_$x/ sensing properties of porous varistors have not been studies in detail. The objective of the present study is to investigate the effect of the composition of the Bi$_2$O$_3$ rich grain boundary phase and other additive such as A1$_2$O$_3$ on the hydrogen gases (H$_2$) sensing properties of porous ZnO based varistors.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.18 no.4
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• pp.12-21
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• 2022

Steam assisted gravity drainage(SAGD) is a process that drills well in the underground oil sands layer, injects hightemperature steam, lowers the viscosity of buried bitumen, and recovers it to the ground. Recently, direct contact steam generator(DCSG) is being developed to maximize steam efficiency for SAGD process. The DCSG requires high technology to achieve pressurized combustion and steam generation in accordance with underground pressurized conditions. Therefore, it is necessary to develop a combustion technology that can control the heat load and exhaust gas composition. In this study, process analysis of high-pressurized DCSG was conducted to apply oxygen enrichment technology in which nitrogen of the air was partially removed for increasing steam production and reducing fuel consumption. As the process analysis conditions, methane as the fuel and normal air or oxygen enriched air as the oxidizing agent were applied to high-pressurized DCSG process model. A simple combustion reaction program was used to calculate the property variations for combustion temperature, steam ratio and residual heat in exhaust gas. As a major results, the steam production efficiency of DCSG using the pure oxygen was about 6% higher than that of the normal air due to the reducing nitrogen in the air. The results of this study will be used as operating data to test the demonstration device.