• 공업화학
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• 제33권6호
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• pp.666-674
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• 2022

The removal efficiencies of nutrients (N and P) and heavy metals (Cu and Ni) by Rhodobacter blasticus and R. blasticus attached to polysulfone carriers, alginate carriers, PVA carriers, and PVA + zeolite carriers in synthetic wastewater were compared. In the comparison of the nutrient removal efficiency based on varying concentrations (100, 200, 500, and 1000 mg/L), R. blasticus + polysulfone carrier treatment showed removal efficiencies of 98.9~99.84% for N and 96.92~99.21% for P. The R. blasticus + alginate carrier treatment showed removal efficiencies of 88.04~97.1% for N and 90.33~97.13% for P. The R. blasticus + PVA carrier treatment showed removal efficiencies of 18.53~44.25% for N and 14.93~43.63% for P. The R. blasticus + PVA + zeolite carrier treatment showed removal efficiencies of 26.65~64.33% for N and 23.44~64.05% for P. In addition, at the minimum inhibitory concentration of heavy metals, R. blasticus (dead cells) + polysulfone carrier treatment showed removal efficiencies of 7.77% for Cu and 12.19% for Ni. Rhodobacter blasticus (dead cells) + alginate carrier treatment showed removal efficiencies of 25.83% for Cu and 31.12% for Ni.

• 한국물환경학회지
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• 제29권1호
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• pp.1-6
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• 2013

This study was focused on improving nitrification efficiencies of M-dephanox (Modified-Dephanox) process. Rotating biological contactor (RBC) was used instead of floating sponge type media in nitrification reactor. High ammonia removal efficiencies were observed in nitrification reactor, regardless of organic loading from contactor of M-dephanox process. Denitrification efficiencies were also increased to maintain low $NO_3-N$ concentration in effluent. This enhanced phosphate release in anaerobic contactor and resulted in high removal efficiencies of phophorus. Average removal efficiencies of $TCOD_{Cr}$ and $SCOD_{Cr}$ were 93.8% and 81.6%, respectively, while those of TKN and ${NH_4}^+-N$ were 80.9% and 74.4%, respectively. As for phosphorous treatment, the average removal efficiencies of TP and OP were 94.7% and 94.3%, respectively. Also, effect of operating temperature on nitrogen removal was examined. Average removal efficiency of TN was 65.8 % at $15^{\circ}C$ or below (at average temperature of $13.3^{\circ}C$), while that was 82.8% at $15^{\circ}C$ or above (at average temperature of $21.9^{\circ}C$).

• 한국환경과학회지
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• 제30권2호
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• pp.161-172
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• 2021

This study was initiated to isolate the microorganisms removing phosphorus (P) from domestic sewage and to investigate the effects of environmental factors on the growth and P removal of the isolated bacteria. Microorganisms isolated from the sewage were identified as Chryseobacterium sp., Stenotrophomonas maltophilia, and Bacillus licheniformis. Among them, Bacillus licheniformis was selected as the P removal microorganism. The environmental factors considered in this study included initial phosphorus concentration, temperature, pH, and carbon source. At initial P concentrations of 10, 20, and 30 mg/L, the P removal efficiencies were 100.0%, 84.0%, and 16.5%, respectively. At 20℃, 30℃, and 40℃, the P removal efficiencies were 0%, 75.8%, and 60.6%, respectively. The removal efficiencies of phosphorus according to pH were 1.6%, 91.7%, and 51.1% at pH 5, pH 7, and pH 9, respectively. Using glucose, acetate, and glucose + acetate as carbon sources yielded P removal efficiencies of 80.9%, 33.6%, and 54.1%, respectively. Therefore, the results from the study demonstrated that the P removal efficiencies of Bacillus licheniformis were the highest when the initial P concentration, temperature, pH, and carbon source were 10 mg/L, 30℃, 7, and glucose, respectively.

• Environmental Engineering Research
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• 제18권1호
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• pp.21-28
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• 2013

In this study, the applicability of visible light-emitting-diodes (LEDs) to the photocatalytic degradation of indoor-level trichloroethylene (TCE) and perchloroethylene (PCE) over N-doped $TiO_2$ (N-$TiO_2$) was examined under a range of operational conditions. The N-$TiO_2$ photocatalyst was calcined at $650^{\circ}C$ (labeled N-650) showed the lowest degradation efficiencies for TCE and PCE, while the N-$TiO_2$ photocatalysts calcined at $350^{\circ}C$, $450^{\circ}C$, and $550^{\circ}C$ (labeled as N-350, N-450, and N-550, respectively) exhibited similar or slightly different degradation efficiencies to those of TCE and PCE. These results were supported by the X-ray diffraction patterns of N-350, N-450, N-550, and N-650. The respective average degradation efficiencies for TCE and PCE were 96% and 77% for the 8-W lamp/N-$TiO_2$ system, 32% and 20% for the violet LED/N-$TiO_2$ system, and ~0% and 4% for the blue LED/N-$TiO_2$ system. However, the normalized photocatalytic degradation efficiencies for TCE and PCE for the violet LED-irradiated N-$TiO_2$ system were higher than those from the 8-W fluorescent daylight lamp-irradiated N-$TiO_2$ system. Although the difference was not substantial, the degradation efficiencies exhibited a decreasing trend with increasing input concentrations. The degradation efficiencies for TCE and PCE decreased with increasing air flow rates. In general, the degradation efficiencies for both target compounds decreased as relative humidity increased. Consequently, it was indicated that violet LEDs can be utilized as energy-efficient light sources for the photocatalytic degradation of TCE and PCE, if operational conditions of N-$TiO_2$ photocatalytic system are optimized.

• 한국물환경학회지
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• 제37권6호
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• pp.483-492
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• 2021

This study evaluated the removal efficiencies of methylene blue (MB) and humic acids (HA) using a rice husk (RH) biochar and powdered activated carbon (PAC). The pseudo-second-order model better presented the adsorption of MB and HA onto a RH biochar than the pseudo-first-order model. Furthermore, better description of the adsorption behavior of MB and HA by the Langmuir isotherm model (R² of the RH biochar: MB = 0.986 and HA = 0.984; R² of PAC: MB = 0.997 and HA = 0.989) than the Freundlich isotherm model (R² of the RH biochar: MB = 0.955 and HA = 0.965; R² of PAC: MB = 0.982 and HA = 0.973) supports the assumption that monolayer adsorption played key roles in the removal of MB and HA using the RH biochar and PAC. Batch experiments were performed on the effects of dosage, temperature, and pH. For all experiments, PAC showed higher efficiencies than RH biochar and MB adsorption efficiencies were higher than those of HA. Adsorption efficiencies increased with increasing amounts of adsorbents and temperature. As the pH increased, adsorption efficiencies of MB were increased while adsorption efficiencies of HA were decreased.

• 한국응용과학기술학회지
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• 제27권3호
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• pp.385-390
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• 2010

This study investigated the decomposition of fenitrothion in Smithion, which is applied on the golf course for pesticide, by the integrated Zero-valent iron(ZVI) and Granular activated carbon(GAC) process. First, the removal efficiencies of the fenitrothion by ZVI and GAC, respectively, were investigated. Second, the removal efficiencies of the fenitrothion by the integrated ZVI and GAC were investigated. The removal efficiencies of fenitrothion by ZVI were higher than those of TOC. The removal efficiencies of fenitrothion and TOC by GAC were similar. As the dosages of ZVI and GAC were increased, the removal efficiencies of fenitrothion and TOC increased. However, as the dosages of ZVI for pretreatment were increased, the adsorptions of fenitrothion on GAC were hindered.

• 한국환경과학회지
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• 제15권7호
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• pp.635-642
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• 2006

Present study evaluated the low-temperature destruction of n-hexane and benzene using mesh-type transition-metal platinum(Pt)/stainless steel(SS) catalyst. The parameters tested for the evaluation of catalytic destruction efficiencies of the two volatile organic compounds(VOC) included input concentration, reaction time, reaction temperature, and surface area of catalyst. It was found that the input concentration affected the destruction efficiencies of n-hexane and benzene, but that this input-concentration effect depended upon VOC type. The destruction efficiencies increased as the reaction time increased, but they were similar between two reaction times for benzene(50 and 60 sec), thereby suggesting that high temperatures are not always proper for thermal destruction of VOCs, when considering the destruction efficiency and operation costs of thermal catalytic system together. Similar to the effects of the input concentration on destruction efficiency of VOCs, the reaction temperature influenced the destruction efficiencies of n-hexane and benzene, but this temperature effect depended upon VOC type. As expected, the destruction efficiencies of n-hexane increased as the surface area of catalyst, but for benzene, the increase rate was not significant, thereby suggesting that similar to the effects of the re- action temperature on destruction efficiency of VOCs, high catalyst surface areas are not always proper for economical thermal destruction of VOCs. Depending upon the inlet concentrations and reaction temperatures, almost 100% of both n-hexane and benzene could be destructed, The current results also suggested that when applying the mesh type transition Metal Pt/SS catalyst for the better catalytic pyrolysis of VOC, VOC type should be considered, along with reaction temperature, surface area of catalyst, reaction time and input concentration.

• 한국환경과학회지
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• 제17권11호
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• pp.1195-1201
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• 2008

Enhancing with non-metallic elemental nitrogen(N) is one of several methods that have been proposed to modify the electronic properties of bulk titanium dioxide($TiO_2$), in order to make $TiO_2$ effective under visible-light irradiation. Accordingly, current study evaluated the feasibility of applying visible-light-induced $TiO_2$ enhanced with N element to cleanse aromatic compounds, focusing on xylene isomers at indoor air quality(IAQ) levels. The N-enhanced $TiO_2$ was prepared by applying two popular processes, and they were coated by applying two well-known methods. For three o-, m-, and p-xylene, the two coating methods exhibited different photocatalytic oxidation(PCO) efficiencies. Similarly, the two N-doping processes showed different PCO efficiencies. For all three stream flow rates(SFRs), the degradation efficiencies were similar between o-xylene and m,p-xylene. The degradation efficiencies of all target compounds increased as the SFR decreased. The degradation efficiencies determined via a PCO system with N-enhanced visible-light induced $TiO_2$ was somewhat lower than that with ultraviolet(UV)-light induced unmodified $TiO_2$, which was reported by previous studies. Nevertheless, it is noteworthy that PCO efficiencies increased up to 94% for o-xylene and 97% for the m,p-xylene under lower SFR(0.5 L $min^{-1}$). Consequently, it is suggested that with appropriate SFR conditions, the visible-light-assisted photocatalytic systems could also become important tools for improving IAQ.

• 한국환경과학회지
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• 제21권11호
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• pp.1321-1331
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• 2012

To date, carbon and nitrogen co-doped photocatalysts (CN-$TiO_2$) for environmental application focused mainly on the aqueous phase to investigate the decomposition of water pollutants. Accordingly, the present study explored the photocatalytic performance of CN-$TiO_2$ photocatalysts for the purification of indoor-level gas-phase aromatic species under different operational conditions. The characteristics of prepared photocatalysts were investigated using X-ray diffraction, scanning emission microscope, diffuse reflectance UV-VIS-NIR analysis, and Fourier transform infrared (FTIR) analysis. In most cases, the decomposition efficiency for the target compounds exhibited a decreasing trend as input concentration (IC) increased. Specifically, the average decomposition efficiencies for benzene, toluene, ethyl benzene, and xylene (BTEX) over a 3-h process decreased from 29% to close to zero, 80 to 5%, 95 to 19%, and 99 to 32%, respectively, as the IC increased from 0.1 to 2.0 ppm. The decomposition efficiencies obtained from the CN-$TiO_2$ photocatalytic system were higher than those of the $TiO_2$ system. As relative humidity (RH) increased from 20 to 95%, the decomposition efficiencies for BTEX decreased from 39 to 5%, 97 to 59%, 100 to 87%, and 100 to 92%, respectively. In addition, as the stream flow rates (SFRs) decreased from 3.0 to 1.0 L $min^{-1}$, the average efficiencies for BTEX increased from 0 to 58%, 63 to 100%, 69 to 100%, and 68 to 100%, respectively. Taken together, these findings suggest that three (IC, RH, and SFR) should be considered for better BTEX decomposition efficiencies when applying CN-$TiO_2$ photocatalytic technology to purification of indoor air BTEX.

• 대한환경공학회지
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• 제39권6호
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• pp.371-376
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• 2017

선회류 약화기(vortex finder)의 구조와 치수를 변형한 7종류의 cyclone을 제작해 PM-10 집진효율 자료를 도출하였고 CFD 분석을 통한 사이클론 입구 속도를 계산하였다. 입구속도는 normal, P, A type 사이클론의 경우 15.48 m/sec, 16.03 m/sec 그리고 15.90 m/sec로 계산되었고 PM-10 집진효율 실험결과는 P tpye과 A type의 사이클론의 경우 normal 사이클론에 비해 4%와 7%의 집진효율이 증가하였다. 또한 평행부의 길이가 증가함에 따라 PM-10의 집진효율은 증가하다 감소하여 집진효율을 최대화 할 수 있는 길이가 존재함을 보여주었다.