Ren X.,Gwangju Institute of Science and Technology |
Shon H.K.,University of Technology, Sydney |
Jang N.,Jeonbuk Development Institute |
Lee Y.G.,Gwangju Institute of Science and Technology |
And 4 more authors.
Water Research | Year: 2010
Conventional and modified membrane bioreactors (MBRs) are increasingly used in small-scale wastewater treatment. However, their widespread applications are hindered by their relatively high cost and operational complexity. In this study, we investigate a new concept of wastewater treatment using a nonwoven fabric filter bag (NFFB) as the membrane bioreactor. Activated sludge is charged in the nonwoven fabric filter bag and membrane filtration via the fabric is achieved under gravity flow without a suction pump. This study found that the biofilm layer formed inside the NFFB achieved 10 mg/L of suspended solids in the permeate within 20 min of initial operation. The dynamic biofilter layer showed good filterability and the specific membrane resistance consisted of 0.3-1.9 × 1012 m/kg. Due to the low F/M ratio (0.04-0.10 kg BOD5/m3/d) and the resultant low sludge yield, the reactor was operated without forming excess sludge. Although the reactor provided aerobic conditions, denitrification occurred in the biofilm layer to recover the alkalinity, thereby eliminating the need to supplement the alkalinity. This study indicates that the NFFB system provides a high potential of effective wastewater treatment with simple operation at reduced cost, and hence offer an attractive solution for widespread use in rural and sparsely populated areas. Crown Copyright © 2009.
Kim S.,Jeonbuk Development Institute |
Choi J.,University of Seoul
KSCE Journal of Civil Engineering | Year: 2013
The study investigates data concerning crashes at roundabouts in order to identify the major factors influencing such events in South Korea. In this investigation, three stages of research tasks were carried out. First, crashes which occurred at South Korean roundabouts were categorized and subsequently compared with international cases. Second, field surveys were conducted in order to investigate how vehicle speeds influence the occurrence of accidents. Third, a statistical analysis was performed in order to investigate the correlation between roundabout geometry and crash occurrences and to reveal major geometric elements of roundabout safety. It was revealed in the study that most vehicles slow down substantially around roundabouts and recover their speed after the roundabouts. Based on the statistical analysis, it was found that negative binomial distribution would give a better performance. In addition, in contrast to cases in the US, the final selection of the independent variables includes as follows: the number of approaches, the number of entering lanes, the entry width, the flare width, the number of circulating lanes and the circulating lane width. Finally, the study provided a model with which to capture the relationship between geometric design elements and the occurrence of crashes at roundabouts. It is anticipated that this model will be applied by engineers to better predict crash occurrences at roundabouts. © 2013 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.
Choi J.S.,University of Seoul |
Kim S.K.,University of Seoul |
Jin M.S.,University of Seoul |
Min D.C.,University of Seoul |
And 2 more authors.
Access Management Theories and Practices - Proceedings of the 2nd International Conference on Access Management, AM 2014 | Year: 2014
This paper presents the result of a study carried out to identify vehicle queue effects of driveway geometry based on statistical analysis of field survey data. The study is necessary to help transportation engineers apply highway access control more efficiently to achieve its full benefits such as diminished queue lengths in main roads as well as in driveways. We applied the multiple regression analysis to establish evidence based on vehicle queues and driveway geometric features. Our research showed that vehicle queues actually vary closely with driveway geometric conditions and that the presence of the speed bump and the crosswalk are the most important factors for increasing vehicle queue lengths. The research findings will contribute to our increased understanding of proper driveway designs when highway access control is the main research interest. © ASCE.
Kim S.,Jeonbuk Development Institute |
Choi J.,University of Seoul |
Lee D.,University of Seoul |
Jang T.,Chonbuk National University
KSCE Journal of Civil Engineering | Year: 2014
This article presents the result of conducting a working model of the Volume to Delay Formula (VDF) that will be applied to analyze the economic feasibility of underground tunnel road projects in Seoul. Without this formula, highway engineers are unable to assess the travel time savings of the underground tunnel road projects, and this troubling situation deters a reasonable progress of this massive plan. To deal with this problem, the research carried out a field survey study in an existing mountain tunnel to capture the characteristics of tunnel traffic flow and conducted a follow-up study to calibrate operational parameters of this tunnel traffic flow. The Golden Section search method was adopted in this purpose and major findings revealed that a reliable VDF could be successfully developed based on the analysis of existing mountain tunnel flows. It was also found that traffic volume levels estimated with existing VDF's and the ones estimated with developed VDF's were much different: a more reasonable volume level was observed across all highway links. We thus concluded that the developed VDF's should be applied to assess travel time savings of the underground tunnel road projects in Seoul. The study results can be applied successfully to six lane tunnels, but more validation efforts are required for other types of tunnels. © 2014 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.
Kim M.S.,Seonam University |
Park S.W.,Seonam University |
Jang N.J.,Jeonbuk Development Institute |
Kwak D.H.,Seonam University
Water Resources | Year: 2016
Innovative water management is the first priority for the Saemangeum Project, a national project for a building global city as a frontrunner of green growth because there has been a big debate concerning the environmental problems (water quality, destruction of mud flats and so on). This study aims at identifying the change of water quality with time and analyzing the cause of its tendency. Results of this study verify that the importance of water quality is required when preparing water infrastructure for smart water use and may use for establishing a proper management plan in the Mangyeong River basins of the Saemangeum. © 2016, Pleiades Publishing, Ltd.