Demonstration of a high throughput on-board hydrogen generation reactor system using aluminum coil as fuel for a vehicle

A novel on-board hydrogen generation concept using Al coil with NaOH was investigated. The reaction rate was successfully controlled by introducing a pumping system for the NaOH solution. The time for the flow to develop fully was mainly dependent on the solution temperature, and the fastest start time recorded was 60 sec at a solution temperature of 70°C. The maximum H₂ generation rate was 200 L min^–1 with a prototype design of the on-board hydrogen generation system 1/8 times the size of a full-size reactor. The H₂ generation process coupled with the solution pumping system was simulated with three-dimensional fluid dynamic software, and the calculated H₂ flow and temperature rise of the system were validated with experimental data.     

Online Water Monitoring Method as a Water Security Tool: A Feasibility View

Since the tragic event on September 11, 2001 (9/11), homeland security has been the center of major attention not only in the United States but also around the world. Among homeland security agenda, more concerns on drinking water system have been drawn into the forefront attention from the public and water industry. Governmental agencies have been called upon to strongly protect the water resources from becoming a possible terror target. The online monitoring of a water system offers the potential to reduce the possible danger from a terrorist contamination as well as from unintentional chemical spills. As potential terrorist contaminants, seven chemical compounds (aldicarb, cycloheximide, dicrotophos, nicotine, sodium arsenate, sodium cyanide, and sodium fluoroacetate) were studied at different doses, in order to determine their detectability when they are present in a water system, including intake, treatment, and distribution. These contaminants were monitored by measuring simple water quality parameters such as conductivity, pH, chlorine residual, turbidity, total organic carbon (TOC), and UV254. Results indicated that the contaminants used for the study were detected at certain toxicity concentrations through the online water quality monitoring method. This method provides a useful tool for watching water resources against possible terror attacks, and also keeping safe water quality.     

An evaluation of indoor and outdoor biological particulate matter

The incidences of allergies, allergic diseases and asthma are increasing world wide. Global climate change is likely to impact plants and animals, as well as microorganisms. The World Health Organization, U.S. Environmental Protection Agency, U.S. Department of Agriculture, U.S. Department of Health and Human Services, and the Intergovernmental Panel on Climate Change cite increased allergic reactions due to climate change as a growing concern. Monitoring of indoor and ambient particulate matter (PM) and the characterization of the content for biological aerosol concentrations has not been extensively performed. Samples from urban and rural North Carolina (NC), and Denver (CO), were collected and analyzed as the goal of this research. A study of PM₁₀ (<10 μm in aerodynamic diameter) and PM_2.5 (<2.5 μm in aerodynamic diameter) fractions of ambient bioaerosols was undertaken for a six month period to evaluate the potential for long-term concentrations. These airborne bioaerosols can induce irritational, allergic, infectious, and chemical responses in exposed individuals. Three separate sites were monitored, samples were collected and analyzed for mass and biological content (endotoxins, (1,3)-β-d-glucan and protein). Concentrations of these bioaerosols were reported as a function of PM size fraction, mass and volume of air sampled. The results indicated that higher concentrations of biologicals were present in PM₁₀ than were present in PM_2.5, except when near-roadway conditions existed. This study provides the characterization of ambient bioaerosol concentrations in a variety of areas and conditions.     

Efforts to develop regulations in Korea similar to the US maximum achievable control technology (MACT) regulations for hazardous waste incinerators

The development of regulations patterned after the United States’ requirement for maximum achievable control technology (MACT) to control hazardous air pollutants from major industrial sources in Korea is in progress. Current management practices and installed air pollution control devices were surveyed; emission tests and continuous emission data collected from facilities under operation were assessed considering other MACT requirements such as reporting, report keeping requirements. Emission sampling and air pollutant analysis were carried out at representative hazardous waste incinerators installed with wet-type and dry-type air pollution control devices. Korean and United States Environmental Protection Agency methods were used for sampling and analysis. The major heavy metals emitted were Zn, Ni, Pb, and Cr. The heavy metal removal efficiency of existing air pollution control devices was greater than 99%. The average mercury removal efficiency was more than 30%. Toluene; m,p-xylene; o-xylene; benzene; dichloromethane; styrene; ethylbenzene; 1,3-dichlorobenzene; and 1,2,4-trimethylbenzene were the major volatile organic compounds emitted. The emissions from field tests were compared, reviewed, and analyzed with respect to MACT regulations to check applicability. Finally, draft guidelines were suggested for effective hazardous air pollutant management in Korea.     

Nitrate and ammonium ions removal from groundwater by a hybrid system of zero-valent iron combined with adsorbents

Nitrate (NO(3)(-)) is a commonly found contaminant in groundwater and surface water. It has created a major water quality problem worldwide. The laboratory batch experiments were conducted to investigate the feasibility of HCl-treated zero-valent iron (Fe(0)) combined with different adsorbents as hybrid systems for simultaneous removal of nitrate (NO(3)(-)) and ammonium (NH(4)(+)) ions from aqueous solution. The maximum NO(3)(-) removal in combined Fe(0)-granular activated carbon (GAC), Fe(0)-filtralite and Fe(0)-sepiolite systems was 86, 96 and 99%, respectively, at 45 °C for 24 h reaction time. The NO(3)(-) removal rate increased with the increase in initial NO(3)(-) concentration. The NO(3)(-) removal efficiency by hybrid systems was in the order of sepiolite > filtralite > GAC. The NH(4)(+) produced during the denitrification process by Fe(0) was successfully removed by the adsorbents, with the removal efficiency in the order of GAC > sepiolite > filtralite. Results of the present study suggest that the use of a hybrid system could be a promising technology for achieving simultaneous removal of NO(3)(-) and NH(4)(+) ions from aqueous solution.     

Distribution and pollution sources of polycyclic aromatic hydrocarbons (PAHs) in reclaimed tidelands and tidelands of the western sea coast of South Korea

The wide-scale reclamation of tidal flats distributed throughout the western and southern coastal areas in Korea has been completed, in an effort to expand the available arable land. The present studies were conducted in order to characterize the concentrations and compositional patterns of selected PAHs, in order to obtain more information regarding environmental risk assessments for sustainable and environment-friendly agriculture in reclaimed tidelands and tidelands in South Korea. The PAH contents were low to moderate, relative to other urbanized regions of the world. Sigma PAHs ranged from 69.8 to 1,175.2 ng g(-1) in dry weight, with a mean value of 394.4 ng g(-1). Differences were observed in the Sigma PAHs concentrations between industrial complex areas and rural regions. The two dominant PAHs were identified as fluoranthene and pyrene. These compounds constituted 1.4 to 55.0% (mean, 33.4%) and 2.7 to 45.6% (mean, 22.0%) of the Sigma PAHs. Our correlation analysis revealed that the Sigma PAHs contents were associated significantly with the organic carbon content (R(2) = 0.86, P < 0.01) and the cation exchange capacity (CEC; R(2) = 0.89, P < 0.01) in the reclaimed tidelands and tidelands.     

Gas-phase elemental mercury removal in a simulated combustion flue gas using TiO2 with fluorescent light

A previously proposed technology incorporating TiO₂ into common household fluorescent lighting was further tested for its Hg⁰ removal capability in a simulated flue-gas system. The flue gas is simulated by the addition of O₂, SO₂, HCl, NO, H₂O, and Hg⁰, which are frequently found in combustion facilities such as waste incinerators and coal-fired power plants. In the O₂ + N₂ + Hg⁰ environment, a Hg⁰ removal efficiency (η_Hg) greater than 95% was achieved. Despite the tendency for η_Hg to decrease with increasing SO₂ and HCl, no significant drop was observed at the tested level (SO₂: 5–300 ppm_v, HCl: 30–120 ppm_v). In terms of NO and moisture, a significant negative effect on η_Hg was observed for both factors. NO eliminated the OH radical on the TiO₂ surface, whereas water vapor caused either the occupation of active sites available to Hg⁰ or the reduction of Hg₀ by free electron. However, the negative effect of NO was minimized (η_Hg > 90%) by increasing the residence time in the photochemical reactor. The moisture effect can be avoided by installing a water trap before the flue gas enters the Hg⁰ removal system.

Implications: This paper reports a novel technology for a removal of gas-phase elemental mercury (Hg⁰) from a simulated flue gas using TiO₂-coated glass beads under a low-cost, easily maintainable household fluorescent light instead of ultraviolet (UV) light. In this study, the effects of individual chemical species (O₂, SO₂, HCl, NO, and water vapor) on the performance of the proposed technology for Hg⁰ removal are investigated. The result suggests that the proposed technology can be highly effective, even in real combustion environments such as waste incinerators and coal-fired power plants.     

Comparison of Fe(VI) (FeO4(2-)) and ozone in inactivating Bacillus subtilis spores

The protozoan parasites such as Cryptosporidiumparvum and Giardialamblia have been recognized as a frequent cause of recent waterborne disease outbreaks because of their strong resistance against chlorine disinfection. In this study, ozone and Fe(VI) (i.e., FeO(4)(2-)) were compared in terms of inactivation efficiency for Bacillus subtilis spores which are commonly utilized as an indicator of protozoan pathogens. Both oxidants highly depended on water pH and temperature in the spore inactivation. Since redox potential of Fe(VI) is almost the same as that of ozone, spore inactivation efficiency of Fe(VI) was expected to be similar with that of ozone. However, it was found that ozone was definitely superior over Fe(VI): at pH 7 and 20°C, ozone with the product of concentration×contact time (CˉT) of 10mgL(-1)min inactivate the spores more than 99.9% within 10min, while Fe(VI) with CˉT of 30mgL(-1) min could inactivate 90% spores. The large difference between ozone and Fe(VI) in spore inactivation was attributed mainly to Fe(III) produced from Fe(VI) decomposition at the spore coat layer which might coagulate spores and make it difficult for free Fe(VI) to attack live spores.     

Decomposition and mineralization of cefaclor by ionizing radiation: kinetics and effects of the radical scavengers

There has been recent growing interest in the presence of antibiotics in different environmental sectors. One considerable concern is the potential development of antibiotic-resistant bacteria in the environment, even at low concentrations. Cefaclor, one of the beta-lactam antibiotics, is widely used as an antibiotic. Kinetic studies were conducted to evaluate the decomposition and mineralization of cefaclor using gamma radiation. Cefaclor, 30 mg/l, was completely degraded with 1,000 Gy of gamma radiation. At a concentration of 30 mg/l, the removal efficiency, represented by the G-value, decreased with increasing accumulated radiation dose. Batch kinetic experiments with initial aqueous concentrations of 8.9, 13.3, 20.0 and 30.0mg/l showed the decomposition of cefaclor using gamma radiation followed a pseudo first-order reaction, and the dose constant increased with lower initial concentrations. At a given radiation dose, the G-values increased with higher initial cefaclor concentrations. The experimental results using methanol and thiourea as radical scavengers indicated that ()OH radicals were more closely associated with the radiolytic decomposition of cefaclor than other radicals, such as e(aq)(-) or ()H. The radical scavenger effects were tested under O(2) and N(2)O saturations for the enhancement of the TOC percentage removal efficiencies in the radiolytic decomposition of cefaclor. Under O(2) saturation, 90% TOC removal was observed with 100,000 Gy. Oxygen is well known to play a considerable role in the degradation of organic substances with effective chain reaction pathways. According to the effective radical reactions, the enhanced TOC percentage removal efficiencies might be based on the fast conversion reactions of e(aq)(-) and ()H with O(2) into oxidizing radicals, such as O(2)(-) and HO(2)(), respectively. 100% TOC removal was obtained with N(2)O gas at 20,000 Gy, as reducing radicals, such as e(aq)(-) and ()H, are scavenged by N(2)O and converted into ()OH radicals, which have strong oxidative properties. The results of this study showed that gamma irradiation was very effective for the removal of cefaclor in aqueous solution. The use of O(2) or N(2)O, with radiation, shows promise as effective radical scavengers for enhancing the TOC or COD removal efficiencies in pharmaceutical wastewaters containing antibiotics. However, the biological toxicity and interactions between various chemicals during the radiolytic treatment, as well as treatments under conditions more representative of real wastewater will require further studies.     

Characterization of cyclohexane and hexane degradation by Rhodococcus sp. EC1

Cyclohexane is a recalcitrant compound that is more difficult to degrade than even n-alkanes or monoaromatic hydrocarbons. In this study, a cyclohexane-degrading consortium was obtained from oil-contaminated soil by an enrichment culture method. Based on a 16S rDNA polymerase chain reaction-denaturing gradient gel electrophoresis method, this consortium was identified as comprising Alpha-proteobacteria, Actinobacteria, and Gamma-proteobacteria. One of these organisms, Rhodococcus sp. EC1, was isolated and shown to have excellent cyclohexane-degrading ability. The maximum specific cyclohexane degradation rate (Vmax) for EC1 was 246 micromol g-DCW(-1) (dry cell weight)h(-1). The optimum conditions of cyclohexane degradation were 25-35 degrees C and pH 6-8. In addition to its cyclohexane degradation abilities, EC1 was also able to strongly degrade hexane, with a maximum specific hexane degradation rate of 361 micromol g-DCW(-1)h(-1). Experiments using 14C-hexane revealed that EC1 mineralized 40% of hexane into CO2 and converted 53% into biomass. Moreover, EC1 could use other hydrocarbons, including methanol, ethanol, acetone, methyl tert-butyl ether, pyrene, diesel, lubricant oil, benzene, toluene, ethylbenzene, m-xylene, p-xylene and o-xylene. These findings collectively suggest that EC1 may be a useful biological resource for removal of cyclohexane, hexane, and other recalcitrant hydrocarbons.