• Journal of Microbiology and Biotechnology
• /
• 제15권3호
• /
• 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.

• 방사성폐기물학회지
• /
• 제21권1호
• /
• pp.1-8
• /
• 2023

The major concern in the deep geological disposal of spent nuclear fuels include sulfide-induced corrosion and stress corrosion cracking of copper canisters. Sulfur diffusion into copper canisters may induce copper embrittlement by causing Cu₂S particle formation along grain boundaries; these sulfide particles can act as crack initiation sites and eventually cause embrittlement. To prevent the formation of Cu₂S along grain boundaries and sulfur-induced copper embrittlement, copper alloys are designed in this study. Alloying elements that can act as chemical anchors to suppress sulfur diffusion and the formation of Cu₂S along grain boundaries are investigated based on the understanding of the microscopic mechanism of sulfur diffusion and Cu₂S precipitation along grain boundaries. Copper alloy ingots are experimentally manufactured to validate the alloying elements. Microstructural analysis using scanning electron microscopy with energy dispersive spectroscopy demonstrates that Cu₂S particles are not formed at grain boundaries but randomly distributed within grains in all the vacuum arc-melted Cu alloys (Cu-Si, Cu-Ag, and Cu-Zr). Further studies will be conducted to evaluate the mechanical and corrosion properties of the developed Cu alloys.

• Journal of Microbiology and Biotechnology
• /
• 제22권8호
• /
• pp.1155-1160
• /
• 2012

Sulfur-utilizing autotrophic denitrification relies on an inorganic carbon source to reduce the nitrate by producing sulfuric acid as an end product and can be used for the treatment of wastewaters containing high levels of nitrates. In this study, sulfur-denitrifying bacteria were used in anoxic batch tests with sulfur as the electron donor and nitrate as the electron acceptor. Various medium components were tested under different conditions. Sulfur denitrification can drop the medium pH by producing acid, thus stopping the process half way. To control this mechanism, a 2:1 ratio of sulfur to oyster shell powder was used. Oyster shell powder addition to a sulfur-denitrifying reactor completely removed the nitrate. Using 50, 100, and 200 g of sulfur particles, reaction rate constants of 5.33, 6.29, and $7.96mg^{1/2}/l^{1/2}{\cdot}h$ were obtained, respectively; and using 200 g of sulfur particles showed the highest nitrate removal rates. For different sulfur particle sizes ranging from small (0.85-2.0 mm), medium (2.0-4.0 mm), and large (4.0-4.75 mm), reaction rate constants of 31.56, 10.88, and $6.23mg^{1/2}/l^{1/2}{\cdot}h$ were calculated. The fastest nitrate removal rate was observed for the smallest particle size. Addition of chemical oxygen demand (COD), methanol as the external carbon source, with the autotrophic denitrification in sufficiently alkaline conditions, created a balance between heterotrophic denitrification (which raises the pH) and sulfur-utilizing autotrophic denitrification, which lowers the pH.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
• /
• pp.261-264
• /
• 2015

Soot particles of diesel and bunker-A with different sulfur contents were generated by pyrolysis with varying conditions of fuel flow rate and residence time in the ceramic tube at $1300^{\circ}C$. TEM and particle size analyzer were used for analysing the primary and the secondary particle size distributions. The results showed that the sulfur content in fuel influences soot inception while the fuel concentration and residence time affects the growth of incepted soot particles.

• 한국응용과학기술학회지
• /
• 제28권4호
• /
• pp.455-463
• /
• 2011

The average sulfur content of crude oil is 2.2%. Coal is about 0.3 to 4.0 percent of the sulfur gases or particles being discharged into the atmosphere through the chimney as 1 to 2% $SO_3$(Sulfur trioxide) and about 95% of the $SO_2$ is reported. $SO_3$ gas, which has many different causes of, as the combustion of sulfur containing fuel during the air due to the excess $SO_2$ gas is oxidized to $SO_3$ gas. Sulfur trioxide emitted from high sulfur heavy oil fired boiler caused white plume in stack and high temperature and cold end corrosion of facilities. So, in order to control sulfur trioxide concentration of Fuel gas in boiler, various of additives are used in other foreign. They are injected to Fuel Oil and consumed in boiler and reduce ash and the conversion rate of sulfur trioxide. In domestic, MgO compounds are used as additives but the total volume of them are made from other foreign company. In this study, MgO compounds were developed with liquid MgO compounds and field application was accomplished. The effect of newly developed chemicals and process were nearly equal to foreign products. In Consequent, the chemicals and process produced by newly developed technology can be substituted for foreign products and reduce the cost of plant operation.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 하계학술대회 논문집
• /
• pp.917-920
• /
• 2001

Effects of addition of manganese and final reduction on segregation behavior of sulfur and final mangetic induction during final annealing have been investigated in the 300 ppm sulfur-contained 3% silicon-iron alloy strips with or without manganese. At the same concentration of sulfur, lower final reduction is favorable for final Goss texture. This is because the probability that the initial Goss grains survive under the highly segregated sulfur atmosphere and grow selectively within the segregated sulfur-free time range becomes higher. In the case of 3% silicon-iron with manganese, much lower magnetic induction was obtained, although the weak final reduction of 30% is given to the alloy, comparative to the 40%. This is because MnS particles acted as an reducer in the primary grain size.

• 한국대기환경학회:학술대회논문집
• /
• 한국대기환경학회 2002년도 춘계학술대회 논문집
• /
• pp.229-230
• /
• 2002

Diesel exhaust particles are mostly sub-micrometer agglomerates composed of carbonaceous primary particles ranging from 10 to 80nm, but contain also adsorbed or condensed hydrocarbons, hydrocarbon derivatives, sulfur compounds, and other materials. If particles are primarily composed of volatile materials, they have different health impacts from solid particles. Thus, the analysis of the volatility of diesel particles is one of an important diesel research area. (omitted)

• Environmental Engineering Research
• /
• 제10권6호
• /
• pp.283-293
• /
• 2005

Characteristics of sulfur-based autotrophic denitrification in a semi-continuous type reactor and the kinetic parameters were studied. Enriched autotrophic denitrifying culture was used for the reactor operation. Biomass growth on sulfur particles and in the liquid medium was monitored using the DAPI staining method. From the result of ion concentration changes and the biomass growth, maximum specific growth rate, ${\mu}_{max}$, and the half velocity constant, $K_M$, were estimated as $0.61\;d^{-1}$ and 3.66 mg/L, respectively. Growth yield coefficient, Y values for electron acceptor and donor were found as 0.49 gVSS/g N and 0.16 gVSS/g S. The biomass showed specific denitrification rate, ranging 0.86-1.13 gN/g VSS-d. A half-order equation was found to best simulate the denitrification process in the packed bed reactor operated in the semi-continuous mode.

• 생명과학회지
• /
• 제21권10호
• /
• pp.1473-1480
• /
• 2011

퍼클로레이트($ClO_4^-$)는 지표수 및 토양/지하수에서 검출되는 오염물이다. 미생물은 퍼클로레이트를 무해한 최종산물로 환원시킬 수 있으므로 퍼클로레이트제거는 미생물을 이용한 방법이 가장 적절한 것으로 알려졌다. 미생물이 퍼클로레이트를 환원시키기 위해서는 전자 공여체가 필요하다. 퍼클로레이트를 환원하기 위한 기존의 기술들은 전자 공여체로서 유기물을 사용하는 종속영양방식의 퍼클로레이트환원세균을 사용한다. 그래서 종속영양 방식으로 퍼클로레이트를 연속 제거하기 위해서는 지속적으로 유기물을 공급해야 하므로 처리비용이 많이 든다. 본 연구에서는 원소 황 입자와 활성 슬러지를 이용하여 독립영양방식의 퍼클로레이트제거가능성을 조사하였다. 입자상 황은 비교적 값이 저렴하고 활성 슬러지는 하수처리장으로부터 쉽게 구할 수 있는 장점이 있다. 회분배양 실험결과 활성 슬러지 미생물은 전자 공여체로서 황 입자가 존재할 때 퍼클로레이트를 제거할 수 있다는 것이 증명되었다. 이러한 퍼클로레이트 분해는 퍼클로레이트가 분해됨에 따라 생성되는 Cl-의 몰 농도를 통해 검증할 수 있었다. 독립영양방식의 $ClO_4^-$ 제거공정에 사용된 황 입자의 표면에 간균 형태의 미생물들이 존재한다는 것을 주사전자현미경을 통해 관찰하였다. 그래서 황 입자가 생물막을 형성하기 위한 담체로도 작용할 수 있다는 것을 알 수 있었다. 황입자가 첨가된 $ClO_4^-$ 분해성 농화 배양으로부터 채취한 생물막의 미생물군집조성은 접종균으로 사용된 활성 슬러지의 그것과는 다름이 DGGE 분석결과 나타났다.

• 대한환경공학회지
• /
• 제32권6호
• /
• pp.555-562
• /
• 2010

수중의 독성을 탐지하기 위하여 황산화미생물을 이용한 새로운 형태의 생태독성탐지 방법이 연구되었다. 황산화미생물이 산소 존재 하에서 황입자를 산화하여 황산을 만들게 되고 이는 EC의 증가 및 pH의 감소를 가져온다. 독성물질이 들어오면 미생물의 저해로 황산을 적게 만들게 되므로 EC의 증가 정도가 감소하게 된다. 인공하천수(EC= 0.12 mS/cm and pH=7.2)를 이용하여 황산화미생물을 배양하고 반응조를 HRT 30분으로 연속 운전한 결과 유출 인공하천수의 EC=0.5~1.2 mS/cm, pH= ~2.5이었으며 7일 동안 일정하게 유지되었다. 이러한 유입수와 유출수의 EC의 차이는 인공하천수가 독성이 없는 조건에서 일정 속도로 황산을 만들었기 때문이다. 아질산성질소 2 mg/L를 함유한 인공하천수를 넣은 결과 인공하천수 주입 후 1.5시간 경과 후 EC 값이 급격하게 감소하고 pH 값은 상승하여 독성을 쉽게 탐지 가능하였다. 최적의 체류시간은 30분이었으며 이는 황입자의 크기를 줄임으로써 더 짧은 체류시간에서 운전이 가능할 것으로 판단된다.