Control of Methyl Tertiary-Butyl Ether via Carbon-Doped Photocatalysts under Visible-Light Irradiation

Lee, Joon-Yeob,Jo, Wan-Kuen Korean Society of Environmental Engineers 2012 Environmental Engineering Research Vol.17 No.4

The light absorbance of photocatalysts and reaction kinetics of environmental pollutants at the liquid-solid and gas-solid interfaces differ from each other. Nevertheless, many previous photocatalytic studies have applied the science to aqueopus applications without due consideration of the environment. As such, this work reports the surface and morphological characteristics and photocatalytic activities of carbon-embedded (C-$TiO_2$) photocatalysts for control of gas-phase methyl tertiary-butyl ether (MTBE) under a range of different operational conditions. The C-$TiO_2$ photocatalysts were prepared by oxidizing titanium carbide powders at $350^{\circ}C$. The characteristics of the C-$TiO_2$ photocatalysts, along with pure TiC and the reference pure $TiO_2$, were then determined by X-ray diffraction, scanning emission microscope, diffuse reflectance ultraviolet-visible-near infrared (UV-VIS-NIR), and Fourier transform infrared spectroscopy. The C-$TiO_2$ powders showed a clear shift in the absorbance spectrum towards the visible region, which indicated that the C-$TiO_2$ photocatalyst could be activated effectively by visible-light irradiation. The MTBE decomposition efficiency depended on operational parameters, including the air flow rate (AFR), input concentration (IC), and relative humidity (RH). As the AFRs decreased from 1.5 to 0.1 L/min, the average efficiencies for MTBE increased from 11% to 77%. The average decomposition efficiencies for the ICs of 0.1, 0.5, 1.0, and 2.0 ppm were 77%, 77%, 54%, and 38%, respectively. In addition, the decomposition efficiencies for RHs of 20%, 45%, 70%, and 95% were 92%, 76%, 50%, and 32%, respectively. These findings indicate that the prepared photocatalysts could be effectively applied to control airborne MTBE if their operational conditions were optimized.

Progress of Multipurpose and Proactive Rainwater Management in Korea

Han, Mooyoung Korean Society of Environmental Engineers 2013 Environmental Engineering Research Vol.17 No.1

Despite the most severe weather and geological conditions, Korean people in earlier times were successful in maintaining sustainable water supplies because they understood the importance of rainwater management, and developed technologies and a philosophy which were needed to live under such circumstances. Recently, the Korean people have suffered frequent incidence of flood damage and drought, and have gradually started to remind themselves of the lessons of the past, which can be described as proactive, multipurpose rainwater management. Most of the problems associated with water and energy can be solved by the integration of rainwater management practices. The concept of multipurpose rainwater management and two examples of its practice are discussed. One is a design for a multipurpose rainwater tank which has been used in a building project, and is based on Korean philosophy. Secondly, a regulation was promulgated recently in Seoul that requires the building of rainwater tanks in new buildings over a certain size. The primary purpose is for the prevention of flooding, but water conservation is a secondary intention. Two examples of proactive rainwater management are discussed, one being public involvement in rainwater management, and the second being the rainwater piggy bank microcredit project. In order to maintain sustainability, to meet the requirements of the Millennium Development Goals, and to be prepared for the effects of climate change, it is expected that multipurpose and proactive rainwater management will be a very effective approach for both developing countries and developed countries. A worldwide network of scientific researchers, as well as a great number of professions, has suggested the promotion of rainwater management.

The Effect of a Rainwater Education Program on South Korean Students' Awareness and Attitudes

Seo, Eun-Jung,Kim, Tae-Yeon,Kang, Tae-Ho Korean Society of Environmental Engineers 2013 Environmental Engineering Research Vol.17 No.1

Recently, rainwater has come to the forefront as an alternative resource contributing to solving various environmental problems, especially those related to water. However, more or less biased perspectives on rainwater as a pollutant, mainly derived from acid rain, have still been pervasive in public as well as research communities. Considering the significance of rain harvesting in recent society, it is necessary to promote educational efforts to overcome such social prejudices and improve desired values towards rainwater. Thus, this research attempted to develop a teaching-learning program focusing on the theme of rainwater for high school students in Korea. To verify the effectiveness of the program, one group pre/post testing was conducted with 57 students participating in the courses. According to the survey, students show significant differences in both awareness and attitude towards rainwater as well as water after the courses. In conclusion, this study has an implication on developing an effective educational way to improve students' positive recognitions and attitudes regarding rainwater-related issues. Such an educational effort might contribute to sharing the worthiness of preserving rainwater with the future generation and promoting rainwater harvesting within wider public participation.

Environmental Engineering Research in September 2012

Seo, Dong-Il Korean Society of Environmental Engineers 2012 Environmental Engineering Research Vol.17 No.3

The Effect of Micro-Pore Configuration on the Flow and Thermal Fields of Supercritical CO₂

Choi, Hang-Seok,Park, Hoon-Chae,Choi, Yeon-Seok Korean Society of Environmental Engineers 2012 Environmental Engineering Research Vol.17 No.2

Currently, the technology of $CO_2$ capture and storage (CCS) has become the main issue for climate change and global warming. Among CCS technologies, the prediction of $CO_2$ behavior underground is very critical for $CO_2$ storage design, especially for its safety. Hence, the purpose of this paper is to model and simulate $CO_2$ flow and its heat transfer characteristics in a storage site, for more accurate evaluation of the safety for $CO_2$ storage process. In the present study, as part of the storage design, a micro pore-scale model was developed to mimic real porous structure, and computational fluid dynamics was applied to calculate the $CO_2$ flow and thermal fields in the micro pore-scale porous structure. Three different configurations of 3-dimensional (3D) micro-pore structures were developed, and compared. In particular, the technique of assigning random pore size in 3D porous media was considered. For the computation, physical conditions such as temperature and pressure were set up, equivalent to the underground condition at which the $CO_2$ fluid was injected. From the results, the characteristics of the flow and thermal fields of $CO_2$ were scrutinized, and the influence of the configuration of the micro-pore structure on the flow and scalar transport was investigated.

Thermal Destruction of Waste Insulating Oil Containing PCBs under High Temperature and Pressurized Conditions

Seok, Min-Gwang,Lee, Gang-Woo,Lee, Jae-Jeong,Kim, Min-Choul,Kim, Yang-Do,Jung, Jong-Hyeon,Shon, Byung-Hyun Korean Society of Environmental Engineers 2012 Environmental Engineering Research Vol.17 No.3

This experimental study was performed to obtain thermal energy from the combustion of synthetic gas, produced by the pyrolysis of insulating oil containing polychlorinated biphenyls (PCBs) in a high temperature and high pressure reactor. The average synthetic gas generated was $59.67Am^3/hr$ via the steady state gasification of insulating oil waste (20 kg/hr) with average concentrations (standard deviation) of $CO_2$, CO, and $H_2$ in the synthetic gas of $38.63{\pm}3.11%$, $35.18{\pm}1.93%$, and $28.42{\pm}1.68%$, respectively. The concentrations of the PCBs in the transformer insulating oil and synthetic gas after its gasification, and the concentrations of the dioxins that could be produced from the incomplete degradation of PCBs were measured. It was revealed that the PCBs in the insulating oil were composed of the series from tetrachlorobiphenyl to octachlorobiphenyl. However, only the #49, #44, #52, and #47/75/48 congeners were detected from the synthetic gas after gasification of the insulating oil and in the flue gas from the combustor. In conclusion, the experimental conditions suggested in this study were very useful for the appropriate treatment of insulating oil containing PCBs. Also, fuel gas containing CO and $H_2$ can be obtained from the pyrolysis of insulating oil containing PCBs.

Assessment of Rainwater Harvesting Potential in Ibadan, Nigeria

Lade, Omolara,Oloke, David Korean Society of Environmental Engineers 2013 Environmental Engineering Research Vol.17 No.1

Recently Ibadan in southwestern Nigeria has been facing severe water shortage due to the increase of population, social and economic activities. In order to meet the shortfall, attempts to utilize rainwater harvesting (RWH) have been made to provide an alternative source of water supply. A desk study was conducted to review various RWH technologies locally, regionally and globally. A hydrological analysis was also carried out using rainfall data for 30 years from two meteorological stations, with the aim of providing a more sustainable RWH system for water supply to private individuals, organizations, and government agencies. RWH is found to be technically feasible based on the prevailing rainfall pattern with over 90% of households having a rooftop constructed from technically appropriate materials. Results of the study indicate that an average roof of $80m^2$ will collect 82,835 L/yr (45 L/person/day) for a family of five people which is about the required water demand for drinking and cooking purposes. Hence, the capacity of storage tanks and the catchment area required for an all-purpose water supply system based on RWH are quite large. These can be reduced to affordable sizes, by collecting and storing water for cooking and drinking only while non-potable uses are supplemented by water from other sources. However, it must be highlighted that due to the type of roofing material, rainwater should go through proper treatment in order to be used for potable purposes. This study clearly shows that Ibadan city has a good rainwater harvesting potential.

Review of Ancient Wisdom of Qanat, and Suggestions for Future Water Management

Taghavi-Jeloudar, Mohsen,Han, Mooyoung,Davoudi, Mohammad,Kim, Mikyeong Korean Society of Environmental Engineers 2013 Environmental Engineering Research Vol.17 No.1

Arid areas have a significant problem with water supply due to climate change and high water demand. More than 3,000 years ago, Persians started constructing elaborate tunnel systems called Qanat for extracting groundwater for agriculture and domestic usages in arid and semi-arid areas and dry deserts. In this paper, it has been demonstrated that ancient methods of water management, such as the Qanat system, could provide a good example of human wisdom to battle with water scarcity in a sustainable manner. The purpose of this paper is twofold: Review of old wisdom of Qanat-to review the history of this ancient wisdom from the beginning until now and study the Qanat condition at the present time and to explore why (notwithstanding that there are significant advantages to the Qanat system), it will no longer be used; and suggestions for future water management-to suggest a number of new methods based on new materials and technology to refine and protect Qanats. With these new suggestions it could be possible to refine and reclaim this method of extracting water in arid areas. Also, a new multi-purpose water management model has been introduced based on rainwater infiltration management over the Qanat system as the model can be applied either in dry or wet cities to solve current urban water problems.

Recovery of Ammonium Salt from Nitrate-Containing Water by Iron Nanoparticles and Membrane Contactor

Hwang, Yu-Hoon,Kim, Do-Gun,Ahn, Yong-Tae,Moon, Chung-Man,Shin, Hang-Sik Korean Society of Environmental Engineers 2012 Environmental Engineering Research Vol.17 No.2

This study investigates the complete removal of nitrate and the recovery of valuable ammonium salt by the combination of nanoscale zero-valent iron (NZVI) and a membrane contactor system. The NZVI used for the experiments was prepared by chemical reduction without a stabilizing agent. The main end-product of nitrate reduction by NZVI was ammonia, and the solution pH was stably maintained around 10.5. Effective removal of ammonia was possible with the polytetrafluoroethylene membrane contactor system in all tested conditions. Among the various operation parameters including influent pH, concentration, temperature, and contact time, contact time and solution pH showed significant effects on the ammonia removal mechanism. Also, the osmotic distillation phenomena that deteriorate the mass transfer efficiency could be minimized by pre-heating the influent wastewater. The ammonia removal rate could be maximized by optimizing operation conditions and changing the membrane configuration. The combination of NZVI and the membrane contactor system could be a solution for nitrate removal and the recovery of valuable products.

Prediction of Chlorophyll-a Changes due to Weir Constructions in the Nakdong River Using EFDC-WASP Modelling

Seo, Dong-Il,Kim, Min-Ae,Ahn, Jong-Ho Korean Society of Environmental Engineers 2012 Environmental Engineering Research Vol.17 No.2

To evaluate the effect of the 4 major rivers restoration project in the Nakdong River to water quality of the river, the Environmental Fluid Dynamics Code (EFDC) and Water Quality Analysis Simulation Program (WASP), are applied in series. Results showed overall decrease in biochemical oxygen demand ($BOD_5$) concentrations and increase in chlorophyll-a concentrations, while total nitrogen and total phosphorous concentrations did not show significant changes, relatively. Decrease in $BOD_5$ concentrations seems to be influenced by an increased hydraulic residence time, which may allow more time for the degradation of organic material. Changes in Chlorophyll-a (Chl-a) concentration, due to the project were more significant for the upper stream areas that show relatively low Chl-a concentration ranges (less than 20 g/L). After the introduction of the Geumho River in the middle part of the Nakdong River, rapid growth of phytoplankton was observed. However, in this middle part of the Nakdong River, the ratio of Chl-a concentration change are less significant, compared to the upper stream areas, due to the project. In the lower stream area, Chl-a concentration decreased after the project. This seems to be resulted from the decreased light availability, due to increased depth, while the nutrient concentrations have been high enough to support phytoplankton growth.