Change in MSW characteristics under recent management strategies in Taiwan

Reduction and recycling initiatives such as producer responsibility and pay-as-you-throw are being implemented in Taiwan. This paper presents a study assessing the impact of recently implemented municipal solid waste (MSW) reduction and recycling management strategies on the characteristics of waste feedstock for incineration in Taiwan. Through the periodic sampling of two typical MSW incineration plants, proximate and ultimate analyses were conducted according to standard methods to explore the influence of MSW reduction and recycling management strategies on incineration feed waste characteristics. It was observed that the annual amount of MSW generated in 2005 decreased by about 10% compared to 2003 and that the characteristics of MSW have changed significantly due to recent management strategies. The heating value of the MSW generated in Taiwan increased yearly by about 5% after program implementation. A comparison of the monthly variations in chemical concentrations indicated that the chlorine content in MSW has changed. This change results from usage reduction of PVC plastic due to the recycling fund management (RFM) program, and the food waste as well as salt content reduction due to the total recycling for kitchen garbage program. This achievement will improve the reduction of dioxin emissions from MSW incineration. In summary, management strategies must be conducted in tandem with the global trend to achieve a zero-waste-discharge country. When implementing these strategies and planning for future MSW management systems, it is important to consider the changes that may occur in the composition and characteristics of MSW over time.     

Estimation and field measurement of methane emission from waste landfills in Hanoi, Vietnam

A methodology for estimating the methane emissions from waste landfills in Hanoi, Vietnam, as part of a case study on Asian cities, was derived based on a survey of documents and statistics related to waste management, interviews with persons in charge, and field investigations at landfill sites. The waste management system in Hanoi was analyzed to evaluate the methane emissions from waste landfill sites. The quantity of waste deposited into the landfill was evaluated from an investigation of the waste stream. The composition of municipal waste was surveyed in several districts in the Hanoi city area, and the quantities of degradable organic waste that had been deposited into landfill for the past 15 years were estimated. Field surveys on methane emissions from landfills of different ages (0.5, 2, and 8 years) were conducted and their methane emissions were estimated to be 120, 22.5, and 4.38 ml/min/m², respectively. The first-order reaction rate of methane generation was obtained as 0.51/year. Methane emissions from waste landfills were calculated by a first-order decay model using this emission factor and the amount of landfilled degradable waste. The estimates of methane emissions using the model accorded well with the estimates of the field survey. These results revealed that methane emissions from waste landfills estimated by regional-specific and precise information on the waste stream are essential for accurately determining the behavior of methane emissions from waste landfills in the past, present, and future.     

Exchange pattern of gaseous elemental mercury in an active urban landfill facility

The environmental behavior of gaseous elemental mercury (Hg) in the ambient air was investigated from the center of a municipal landfill site (area approximately 0.6km(2)) located in Dae Gu, Korea in the winter of 2004. In order to provide insight on the Hg exchange processes in strong source areas, we continuously analyzed Hg concentration gradients developed across two heights between 1m and 5m over soil surfaces at hourly intervals. The results displayed Hg concentrations in the lower and upper levels in the range of 1.46-13.1ngm(-3) (3.33+/-1.29ngm(-3): N=139) and 1.20-13.7ngm(-3) (3.27+/-1.23ngm(-3): N=139), respectively. The results of our analysis, when divided separately into emission and dry deposition, showed that emission of Hg was fairly dominant in frequency (up to 58%) over dry deposition. By multiplying our Hg gradient data with the K-values predicted indirectly from the results of previous studies, the emission and deposition fluxes of Hg were estimated as 39.0+/-43.3ngm(-2)h(-1) (N=80) and -60.0+/-80.2ngm(-2)h(-1) (N=59), respectively. Although the magnitudes of exchange were moderately lower than previously investigated anthropogenic sources, the overall results of this study suggest that an active landfill site can act as an important source of Hg in an urban environment along with other man-made activities.     

Modeling of metal binding in tropical Fluvisols and Acrisols treated with biosolids and wastewater

There is growing concern about the accumulation of metals in tropical agricultural soils. In this study, experimental results from batch studies were used to test whether multi-surface geochemical models could describe metal binding in selected Vietnamese soils. The multi-surface models considered metal binding to iron hydroxides (using the diffuse layer model), organic matter (Stockholm Humic model and NICA-Donnan model), and phyllosilicate clay (Gaines-Thomas equation) as well as complexation to dissolved organic and inorganic ligands in the solution phase. We found that for total dissolved Cd, Cu and Zn the two multi-surface models being tested provided very good model fits for all soils, as evidenced by low root-mean square errors between model predictions and observations. These results suggest that organic matter is an important sorbent for many metals in these soils. However, poor fits were obtained for Cr(III), Mn and Pb for all soils. The study also suggests that the pH is the main factor that controls the solubility of metals in tropical Fluvisols and Acrisols subjected to application of biosolids and wastewater, and that advanced multi-surface models can be used to simulate the binding and release of many trace metals.     

Occurrence, fate and antibiotic resistance of fluoroquinolone antibacterials in hospital wastewaters in Hanoi, Vietnam

Occurrence and behavior of fluoroquinolone antibacterial agents (FQs) were investigated in hospital wastewaters in Hanoi, Vietnam. Hospital wastewater in Hanoi is usually not treated and this untreated wastewater is directly discharged into one of the wastewater channels of the city and eventually reaches the ambient aquatic environment. The concentrations of the FQs, ciprofloxacin (CIP) and norfloxacin (NOR) in six hospital wastewaters ranged from 1.1 to 44 and from 0.9 to 17 micrgl(-1), respectively. Total FQ loads to the city sewage system varied from 0.3 to 14 g d(-1). Additionally, the mass flows of CIP and NOR were investigated in the aqueous compartment in a small wastewater treatment facility of one hospital. The results showed that the FQ removal from the wastewater stream was between 80 and 85%, probably due to sorption on sewage sludge. Simultaneously, the numbers of Escherichia coli (E. coli) were measured and their resistance against CIP and NOR was evaluated by determining the minimum inhibitory concentration. Biological treatment lead to a 100-fold reduction in the number of E. coli but still more than a thousand E. coli colonies per 100ml of wastewater effluent reached the receiving water. The highest resistance was found in E. coli strains of raw wastewater and the lowest in isolates of treated wastewater effluent. Thus, wastewater treatment is an efficient barrier to decrease the residual FQ levels and the number of resistant bacteria entering ambient waters. Due to the lack of municipal wastewater treatment plants, the onsite treatment of hospital wastewater before discharging into municipal sewers should be considered as a viable option and consequently implemented.     

Bioaccessibility of polychlorinated biphenyls in different foods using an in vitro digestion method

Bioaccessibility of organic pollutants in food is important for exposure estimation and risk assessment. An in vitro enzyme digestion experiment was carried out to analyze the bioaccessibility of PCBs in different foods including freshwater fish (bighead carp and oriental weather fish) and vegetables (spinach and cabbage). The results indicated that the bioaccessibility of PCBs in freshwater fish (3%) was much lower than that in leafy vegetables (25%). Based on field survey, the daily exposure TEQ value from these two types of food was 17.9 pg/kg bw/day. However, when bioaccessibility was taken into consideration, the value decreased to 0.61 pg/kg bw/day. Therefore, the forms of PCBs existing in food strongly influenced the bioavailability for humans, which may have important implications on dietary exposure. To our knowledge, this is the first paper to illustrate the bioaccessibility of PCBs in different foods using an in vitro digestion method.     

美国高校实验室废弃物安全管理浅析

实验室废弃物的收集、管理不当会造成严重的环境污染甚至人员伤害,这已经引起国内外相关部门的高度重视。美国高校在实验室废弃物安全管理方面积累了科学、规范的管理经验：通过对实验室科研人员的专业培训保证废弃物的安全分类收集;通过专业环境健康安全管理部门人员的科学管理实现对废弃物的安全收集与存放;通过专业废弃物收集处置公司来实现废弃物的安全转移运输和最终无害化处理。为加强国内高校实验室废弃物的安全管理,在对美国高等院校实验室废弃物的收集、储藏、运输和处理等方面调查研究的基础上,结合国内实验室废弃物安全管理的现状,对国内外高校实验室废弃物的安全管理进行了对比分析,以期为国内高校实验室废弃物的安全管理工作提供有益的借鉴。     

Investigation of fluorescence characterization and electrochemical behavior on the catalysts of nanosized Pt-Rh/γ-Al2O3 to oxidize gaseous ammonia

This work describes the environmentally friendly technology for oxidation of ammonia (NH₃) to form nitrogen at temperatures range from 423K to 673K by selective catalytic oxidation (SCO) over a nanosized Pt-Rh/γ-Al₂O₃ catalyst prepared by the incipient wetness impregnation method of hexachloroplatinic acid (H₂PtCl₆) and rhodium (III) nitrate (Rh(NO₃)₃) with γ-Al₂O₃ in a tubular fixed-bed flow quartz reactor (TFBR). The characterization of catalysts were thoroughly measured using transmission electron microscopy (TEM), threedimensional excitation-emission fluorescent matrix (EEFM) spectroscopy, UV-Vis absorption, dynamic lightscattering (DLS), zeta potential meter, and cyclic voltammetry (CV). The results demonstrated that at a temperature of 673K and an oxygen content of 4%, approximately 99% of the NH₃ was removed by catalytic oxidation over the nanosized Pt-Rh/γ-Al₂O₃ catalyst. N₂ was the main product in NH₃-SCO process. Further, it reveals that the oxidation of NH₃ was proceeds by the over-oxidation of NH₃ into NO, which was conversely reacted with the NH₃ to yield N₂. Therefore, the application of nanosized Pt-Rh/γ-Al₂O₃ catalyst can significantly enhance the catalytic activity toward NH₃ oxidation. One fluorescent peak for fresh catalyst was different with that of exhausted catalyst. It indicates that EEFM spectroscopy was proven to be an appropriate and effective method to characterize the Pt clusters in intrinsic emission from nanosized Pt-Rh/γ-Al₂O₃ catalyst. Results obtained from the CV may explain the significant catalytic activity of the catalysts.     

WINTER HEAT BUDGET AND FRAZIL ICE PRODUCTION IN THE UPPER ST. LAWRENCE RIVER1

ABSTRACT: Winter heat budget and frazil ice production in the St. Lawrence River between the Ogdensburg-Prescott Boom and the Moses-Saunders Power Dam are analyzed. Contributions of each heat exchange component, and spatial distributions of heat exchange rates are calculated for three typical winters. Based on the calculated heat budget, the amount and distribution of frazil ice generated in the study reach is analyzed. The result of this study indicates that the thermal energy contained in the river water flowing into the study reach is a dominate factor in the heat budget analysis. The heat flux from the channel bottom accounts for an important portion of the total heat budget during the ice covered period.