Development of pseudo-amphoteric sponge media using polyalkylene oxide-modified polydimethylsiloxane (PDMS) for rapid start-up of wastewater treatment plant

Hydrophobic sponge media require a relatively long start-up period, as they just float on the surface of aeration tanks due to their little tendency to adsorb water, which causes a delay in the initiation of bacterial attachment. In order to overcome this difficulty, a new pseudo-amphoteric BioCube media (a standard BioCube is hydrophobic) using polyalkylene oxide-modified polydimethylsiloxane (PDMS) as a surfactant was developed. Of the many evaluated hydrophilizing agents, polyalkylene oxide-modified PDMS was found suitable. Among the diverse types of modified PDMS, the non-reactive polyethylene oxide-modified PDMS was found to be optimum agent. Pseudo-amphoteric BioCube media are readily immersible, but after complete immersion, they gradually become hydrophobic, as the polyethylene oxide-modified PDMS is designed to alienate from polyurethane backbone of BioCube to provide hydrophobic surfaces exhibiting more affinity for bacterial attachment. Clearly, the pseudo-amphoteric BioCube showed faster bacterial attachment during the early stage due to chances of enhanced contact between the bacteria and media surfaces, but the extent of attachment between the hydrophobic and pseudo-amphoteric BioCube was similar at the steady state because the former (pseudo-amphoteric BioCube) had already changed to hydrophobic. Fluorescent in situ hybridization result showed 14% occupation by ammonia oxidizing bacteria, 13% by nitrite oxidizing bacteria and 73% by others in pseudo-amphoteric BioCube, respectively.     

Economic and environmental optimization of a multi-site utility network for an industrial complex

Most chemical companies consume a lot of steam, water and electrical resources in the production process. Given recent record fuel costs, utility networks must be optimized to reduce the overall cost of production. Environmental concerns must also be considered when preparing modifications to satisfy the requirements for industrial utilities, since wastes discharged from the utility networks are restricted by environmental regulations. Construction of Eco-Industrial Parks (EIPs) has drawn attention as a promising approach for retrofitting existing industrial parks to improve energy efficiency. The optimization of the utility network within an industrial complex is one of the most important undertakings to minimize energy consumption and waste loads in the EIP.In this work, a systematic approach to optimize the utility network of an industrial complex is presented. An important issue in the optimization of a utility network is the desire of the companies to achieve high profits while complying with the environmental regulations. Therefore, the proposed optimization was performed with consideration of both economic and environmental factors.The proposed approach consists of unit modeling using thermodynamic principles, mass and energy balances, development of a multi-period Mixed Integer Linear Programming (MILP) model for the integration of utility systems in an industrial complex, and an economic/environmental analysis of the results. This approach is applied to the Yeosu Industrial Complex, considering seasonal utility demands. The results show that both the total utility cost and waste load are reduced by optimizing the utility network of an industrial complex.     

Atmospheric versus lithogenic contribution to the composition of first- and second-order stream waters in Seoul and its vicinity

The spatial variations in the chemistry of first- and second-order stream waters (N = 65) were investigated in the easterly bound of Seoul in order to assess the effects of urban air pollution on surface water chemistry. The sulfate (SO4(2-)) was high (range 3.9-17.8 mg l(-1), mean 11.8 mg l(-1)) within 30 km away from the center of Seoul, compared to the levels (range 1.1-7.7 mg l(-1), mean 4.3 mg l(-1)) observed in remote areas (30-70 km away). Both graphical examination and statistical evaluation (variogram) of sulfate concentration data consistently showed the decrease of sulfate concentration with increasing distance. The results of mass balance modeling also indicate that the concentrations of SO4(2-), Cl- and Na+ may be affected mainly by dry/wet deposition. However, the spatial variations of major cations such as Ca2+ and Na+ are well explained by the reaction of rainwater with diverse rocks in the watercourse. The water type was found to change from Ca(-Na)-SO4) type to Ca(-a)-HCO3 type with the increasing distance. It is thus inferred that the pollutants like SO2 emitted from strong man-made source areas of Seoul are transported to the considerable distance (at least 30 km away) by westerlies and that such mechanism may lead to the changes of the anion composition in surface water. In the remote area (> 30 km away from Seoul), the stream water chemistry appears to be influenced more effectively by the weathering of rock-forming minerals.     

Epidemiology of musculoskeletal symptoms among Korean hospital nurses.

We investigated the epidemiology of musculoskeletal symptoms (MSS) among a complete cross-section of 330 nurses from a large Korean hospital, by means of a questionnaire survey (response rate: 97.9%). The prevalence of MSS at any body site was 93.6%, with symptoms most commonly reported at the shoulder (74.5%), lower back (72.4%), neck (62.7%), lower legs (52.1%) and hand/wrist (46.7%). Logistic regression indicated that nurses who undertook manual handling of patients were 7.2 times as likely to report MSS (OR 7.2, 95%CI 1.2-42.3, P = .0275), while nurses suffering from periodic depression experienced a 3.3-fold MSS risk (OR 3.3, 95%CI 1.3-8.3, P = .0104). Overall, our study suggests that Korean nurses incur a very high MSS burden when compared internationally. A greater commitment is needed to improve physical conditions, occupational tasks and psychosocial work issues among nurses in this country.     

Two facets of conscientiousness and the knowledge sharing dilemmas in the workplace: Contrasting moderating functions of supervisor support and coworker support

This study adopts self‐ and other‐centered approaches to explain how the two facets of conscientiousness (i.e., dutifulness and achievement striving) distinctly resolve knowledge sharing dilemmas among employees. It also explores how the critical social surroundings of employees (i.e., supervisor support and coworker support) neutralize or activate the effects of dutifulness and achievement striving on knowledge‐sharing behavior. Our analysis of the data collected from 150 employee–supervisor dyads corroborates that the other‐centered facet of conscientiousness (dutifulness) is positively related to knowledge‐sharing behavior, whereas the self‐centered facet (achievement striving) is negatively related to the same behavior. The analysis also affirms that the positive effect of dutifulness and the negative effect of achievement striving on knowledge sharing are strengthened when supervisor support is low and coworker support is high. This study offers theoretical and practical implications relevant to knowledge management in organizations, distinct roles of facet‐specific personalities toward knowledge sharing, and contrasting personality–situation interactions by situation strength and trait activation in shaping employee behavior.     

Baseline Study on Essential and Trace Elements in Polished Rice from South Korea

In 2000, 63 (polished) white rice samples were collected in eight administrative areas all over South Korea and analyzed for 16 elements by inductively coupled plasma atomic emission spectrometry (ICP-AES). Potassium had the highest content, next to Mg, Ca, Si, Zn, Na, Al and Fe. Most of the samples contained worldwide average concentrations of essential and trace elements in rice grains reported by various researches. For inter-area differences in those elements in the rice, the statistical analysis showed no significant differences (p > 0.05) among the eight administrative areas, suggesting that inter-area differences were not substantial in most cases. Thus, the present data can be used as national background levels of elements in rice produced in South Korea. Using the published data on daily consumption of rice in South Korea, it was possible to estimate the daily intake of As, Cd, Cu, Pb and Zn via rice. The results showed that a regular consumption of rice produced in Korea plays an important role in accumulation of essential and trace elements in Korean, especially for farm-households consuming relatively large amounts of rice.     

SynGas production from organic waste using non-thermal-pulsed discharge

The purpose of this study was to develop a technology that can convert biogas to synthesis gas (SynGas), a low-emission substituted energy, using a non-thermal-pulsed plasma method. To investigate the characteristics of SynGas production from simulated biogas, the reforming characteristics in relation to variations in pulse frequency, biogas component ratio (C3H8/CO2), vapor flow ratio (H2O/total flow rate [TFR]), biogas velocity, and pulse power were studied. A maximum conversion rate of 49.1% was achieved for the biogas when the above parameters were 500 Hz, 1.5, 0.52, 0.32 m/sec, and 657 W, respectively. Under the above conditions, the dry basis mole fractions of the SynGas were as follows: H2 = 0.645, CH4 = 0.081, C2H2 = 0.067, C3H6 = 0.049, CO = 0.008 and C2H4 = 0.004. The ratio of hydrogen to the other intermediates in the SynGas (H2/ITMs) was 3.1.     

Probability mass first flush evaluation for combined sewer discharges

The Korea government has put in a lot of e ort to construct sanitation facilities for controlling non-point source pollution. The first flush phenomenon is a prime example of such pollution. However, to date, several serious problems have arisen in the operation and treatment e ectiveness of these facilities due to unsuitable design flow volumes and pollution loads. It is di cult to assess the optimal flow volume and pollution mass when considering both monetary and temporal limitations. The objective of this article was to characterize the discharge of storm runo pollution from urban catchments in Korea and to estimate the probability of mass first flush (MFFn) using the storm water management model and probability density functions. As a result of the review of gauged storms for the representative using probability density function with rainfall volumes during the last two years, all the gauged storms were found to be valid representative precipitation. Both the observed MFFn and probability MFFn in BE-1 denoted similarly large magnitudes of first flush with roughly 40% of the total pollution mass contained in the first 20% of the runo . In the case of BE-2, however, there were significant di erence between the observed MFFn and probability MFFn.     

A new synthesis of tetrachlorofluorodibenzo‐p‐dioxin

Abstract

The 1,2,3,4‐tetrachloro‐7‐fluorodibenzo‐p‐dioxin has been synthesized via condensation of 4‐fluorocatechol and pentachloronitrobenzene. This compound could be used as an internal standard for the analysis of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin by Chromatographic methods.