Performance of an electrochemical COD (chemical oxygen demand) sensor with an electrode-surface grinding unit

An electrochemical COD (chemical oxygen demand) sensor using an electrode-surface grinding unit was investigated. The electrolyzing (oxidizing) action of copper on an organic species was used as the basis of the COD measuring sensor. Using a simple three-electrode cell and a surface grinding unit, the organic species is activated by the catalytic action of copper and oxidized at a working electrode, poised at a positive potential. When synthetic wastewater was fed into the system, the measured Coulombic yields were found to be dependent on the COD of the synthetic wastewater. A linear correlation between the Coulombic yields and the COD of the synthetic wastewater was established (10-1000 mg L(-1)) when the electrode-surface grinding procedure was activated briefly at 8 h intervals. When various kinds of wastewater samples obtained from various sewage treatment plants were measured, linear correlations (r(2)> or = 0.92) between the measured EOD (electrochemical oxygen demand) value and COD of the samples were observed. At a practical wastewater treatment plant, the measurement system was successfully operated with high accuracy and good stability over 3 months. These experimental results show that the application of the measurement system would be a rapid and practical method for the determination of COD in water industries.     

Reliable evidences that the removal mechanism of hexavalent chromium by natural biomaterials is adsorption-coupled reduction

For the last few decades, over 200 papers have been published in the Cr(VI) biosorption research field. Most early studies have claimed that Cr(VI) was removed from aqueous phase through an anionic adsorption, but this approach has been lost old original position. It has been newly explained that these findings were misinterpreted due to errors in measuring the concentrations of different chromium species in the aqueous phase, insufficient contact time required for equilibrium and the lack of information about the oxidation state of the chromium bound to biomaterials. Although 'adsorption-coupled reduction' is now widely accepted as the mechanism of Cr(VI) biosorption by natural biomaterials, a number of researchers still believe that Cr(VI) is removed by anionic adsorption onto the biomaterials. Therefore, the objective of this study was to show reliable evidences that the removal mechanism of Cr(VI) by natural biomaterials is 'adsorption-coupled reduction'. Sixteen natural biomaterials were used to study the Cr(VI) biosorption. Not only Cr(VI) but also total Cr in the aqueous phase were analyzed. X-ray photoelectron spectroscope was also used to verify the oxidation state of the chromium bound to the biomaterials. Finally, the removal behavior of Cr(VI) by each biomaterial was described by a kinetic model based on a redox reaction.     

Estimation of methane emission potential using the Clean Development Mechanism (CDM) tool for municipal solid waste landfill in Mandalay,Myanmar

Journal of Material Cycles and Waste Management - Municipal solid waste (MSW) landfills are the third largest source of global methane emissions as biogas (11%). In developing countries, MSW...     

First-trimester screening for Down syndrome; the role of nasal bone assessment in the Korean population

Objectives The aim of this study was to evaluate the role of nasal bone assessment in first-trimester screening for Down syndrome (DS) in the Korean population. Methods From July 2004 to March 2006, we prospectively evaluated the fetal nasal bones at 11–14 weeks' gestation in the Korean population. Results A successful evaluation was possible in 6490 of 6787 fetuses (95.6%). Absent, hypoechoic, and short nasal bones were seen in 4 (26.7%), 4 (26.7%), and 1 (6.7%) of 15 fetuses with DS, respectively, whereas in 5 (0.1%), 11 (0.2%), and 246 (3.8%) of 6456 normal fetuses. The incidence of absent and hypoechoic nasal bone showed significant differences between normal fetuses and fetuses with DS (P < 0.0005, both). Screening for DS using an absent or hypoechoic nasal bone resulted in a sensitivity of 53.3%, a specificity of 99.8%, a positive likelihood ratio of 215.2, and a negative likelihood ratio of 0.5. Conclusion Our study showed that nasal bone abnormality at 11–14 weeks of gestation had a high association with DS in the Korean population. This suggests that nasal bone assessment can be used to supplement the current first-trimester screening for DS in the Korean population. Copyright © 2007 John Wiley & Sons, Ltd.     

Influence of aeration rate and reactor shape on the composting of poultry manure and sawdust

To achieve successful composting, all the biological, chemical, and physical characteristics need to be considered. The investigation of our study was based on various physicochemical properties, i.e., temperature, ammonia concentration, carbon dioxide concentration, pH, electrical conductivity (EC), carbon/nitrogen (C/N) ratio, organic matter (OM) content, moisture content, bacterial population, and seed germination index (GI), during the composting of poultry manure and sawdust for different aeration rates and reactor shapes. Three cylindrical-shaped and three rectangular-shaped pilot-scale 60-L composting reactors were used in this study, with aeration rates of 0.3 (low), 0.6 (medium), and 0.9 (high) L min^?1 kg^?1 DM (dry matter). All parameters were monitored over 21 days of composting. Results showed that the low aeration rate (0.3 L min^?1 kg^?1 DM) corresponded to a higher and longer thermophilic phase than did the high aeration rate (0.9 L min^?1 kg^?1 DM). Ammonia and carbon dioxide volatilization were directly related to the temperature profile of the substrate, with significant differences between the low and high aeration rates during weeks 2 and 3 of composting but no significant difference observed during week 1. At the end of our study, the final values of pH, EC, moisture content, C/N ratio, and organic matter in all compost reactors were lower than those at the start. The growth rates of mesophilic and thermophilic bacteria were directly correlated with mesophilic and thermophilic conditions of the compost. The final GI of the cylindrical reactor with an airflow rate of 0.3 L min^?1 kg^?1 DM was 82.3%, whereas the GIs of the other compost reactors were below 80%. In this study, compost of a cylindrical reactor with a low aeration rate (0.3 L min^?1 kg^?1 DM) was more stable and mature than the other reactors.

Implications: The poultry industry is growing in South Korea, but there are problems associated with the management of poultry manure, and composting is one solution that could be valuable for crops and forage if managed properly. For high-quality composting, the aeration rate in different reactor shapes must be considered. The objective of this study was to investigate various physicochemical properties with different aeration rates and rector shapes. Results showed that aeration rate of 0.3 L min^?1 kg^?1 DM in a cylindrical reactor provides better condition for maturation of compost.     

Temperature and salinity adaptation in the purple shore crab Hemigrapsus nudus: An in vitro metabolic flux study with excised gills

The effects of temperature and salinity acclimation on intermediary metabolism in excised gill homogenates from Hemigrapsus nudus were examined. In general, a decrease in salinity was followed by an increase in the oxidation of the substrates glucose-1-¹⁴C, acetate-1-¹⁴C and glycine-¹⁴C to ¹⁴CO₂. Also, there was an increase in amino acid incorporation into the protein fraction. Both of these metabolic parameters were differentially temperature-sensitive. An enzymic model which may explain the increase in respiration rate observed in several intertidal invertebrates meeting an hypo-osmotic stress is proposed, using data from these experiments and also from the literature.     

Possible particulate nitrite formation and its atmospheric implications inferred from the observations in Seoul,Korea

Simultaneous measurements of gaseous species and fine-mode, particulate inorganic components were performed at the University of Seoul, Seoul in Korea. In the simultaneous measurements, a certain level of nitrous acid (HONO) was observed in the gas-phase, indicating possible heterogeneous HONO production on the surface of the ambient aerosols. On the other hand, high particulate nitrite (NO^2?) concentrations of 1.41(±2.26) μg/m³ were also measured, which sometimes reached 18.54 μg/m³. In contrast, low HONO-to-NO₂ ratios of 0.007(±0.006) were observed in Seoul. This indicates that a significant fraction of HONO is dissolved in atmospheric aerosols. Around the Seoul site, sufficient alkalinity may have been provided to the atmospheric aerosols from the excessive presence of NH₃ in the gas-phase. Due to the alkaline particulate conditions (defined in this study as a particle pH >～3.29), the HONO molecules produced at the surface of the atmospheric aerosols appeared to have been converted into particulate nitrite, thereby preventing their further participation in the atmospheric O₃/NO_y/HO_x photochemical cycles. It was estimated that a minimum average of 65% of HONO was captured by alkaline, anthropogenic, urban particles in the Seoul measurements.     

A Preliminary Study of Modeling the Air Pollution Effects fromTraffic Engineering Alternatives

Three separate mathematical models were combined to calculate the changes in carbon monoxide (CO) concentrations that might result from traffic engineering changes. The three models used were: (1) The Dynamic Highway Transportation model (DHTM) which relates traffic flow patterns to physical parameters and traffic signal characteristics of a network; (2) an emission model that predicts CO emissions from traffic flow parameters such as number of stops, idling time, etc; and (3) the APRAC-1A urban diffusion model which calculates CO concentrations from source distributions and meteorological factors. The composite model was applied to traffic in downtown Chicago for a specific set of meteorological conditions. Results are compared for two traffic signal control schemes. In those blocks where concentrations were highest, the model indicates a 20% reduction is possible through improved traffic signal controls. The model should be useful for testing other traffic control measures.     

Environmental assessment on a soil washing process of a Pb-contaminated shooting range site: a case study

In this study, an environmental assessment on a soil washing process for the remediation of a Pb-contaminated shooting range site was conducted, using a green and sustainable remediation tool, i.e., SiteWise ver. 2, based on data relating specifically to the actual remediation project. The entire soil washing process was classified into four major stages, consisting of soil excavation (stage I), physical separation (stage II), acid-based (0.2 N HCl) chemical extraction (stage III), and wastewater treatment (stage IV). Environmental footprints, including greenhouse gas (GHG) emissions, energy consumption, water consumption, and critical air pollutant productions such as PM₁₀, NO _x , and SO _x , were calculated, and the relative contribution of each stage was analyzed in the environmental assessment. In stage I, the relative contribution of the PM₁₀ emissions was 55.3 % because the soil excavation emitted the fine particles. In stage II, the relative contribution of NO _x and SO _x emissions was 42.5 and 52.5 %, respectively, which resulted from electricity consumption for the operation of the separator. Stage III was the main contributing factor to 63.1 % of the GHG emissions, 67.5 % of total energy used, and 37.4 % of water consumptions. The relatively high contribution of stage III comes from use of consumable chemicals such as HCl and water-based extraction processes. In stage IV, the relative contributions of GHG emissions, total energy used, and NO _x and SO _x emissions were 23.2, 19.4, 19.5, and 25.3 %, respectively, which were caused by chemical and electricity demands for system operation. In conclusion, consumable chemicals such as HCl and NaOH, electric energy consumption for system operation, and equipment use for soil excavation were determined to be the major sources of environmental pollution to occur during the soil washing process. Especially, the acid-based chemical extraction process should be avoided in order to improve the sustainability of soil washing processes.