Comparative studies on toluene removal and pressure drop in biofilters using different packing materials

To select the best available packing material for malodorous organic gases such as toluene and benzene, biofilter performance was compared in biofilters employed different packing materials including porous ceramic (celite), Jeju scoria (lava), a mixture of granular activated carbon (GAC) and celite (GAC/celite), and cubic polyurethane foam (PU). A toluene-degrading bacterium, Stenotrophomonas maltophilia T3-c, was used as the inoculum. The maximum elimination capacities in the celite, lava, and GAC/celite biofilters were 100, 130, and 110 gm(-3) hr(-1), respectively. The elimination capacity for the PU biofilter was approximately 350 g m(-3) hr(-1) at an inlet loading of approximately 430 g m(-3) hr(-1), which was 2 to 3.5 times higher than for the other biofilters. The pressure drop gradually increased in the GAC/ celite, celite and lava biofilters after 23 day due to bacterial over-growth, and the toluene removal efficiency remarkably decreased with increasing pressure drop. Backwashing method was not effective for the control of biomass in these biofilters. In the PU biofilter however, backwashing allowed maintenance of a pressure drop of 1 to 3 mm H2O m(-1) and a removal efficiency of > 80%, indicating that the PU was the best packing material for toluene removal among the packing materials tested.     

Bioreduction of nitrate in groundwater using a pilot-scale hydrogen-based membrane biofilm reactor

A long-term pilot-scale H₂-based membrane biofilm reactor (MBfR) was tested for removal of nitrate from actual groundwater. A key feature of this second-generation pilot MBfR is that it employed lower cost polyester hollow fibers and still achieved high loading rate. The steady-state maximum nitrate surface loading at which the effluent nitrate and nitrite concentrations were below the Maximum Contaminant Level (MCL) was at least 5.9 g·N·(m²·d)^?1, which corresponds to a maximum volumetric loading of at least 7.7 kg·N·(m³·d) ^?1. The steady-state maximum nitrate surface area loading was higher than the highest nitrate surface loading reported in the first-generation MBfRs using composite fibers (2.6 g·N·(m²·d)^?1). This work also evaluated the H₂-utilization efficiency in MBfR. The measured H₂ supply rate was only slightly higher than the stoichiometric H₂-utilization rate. Thus, H₂ utilization was controlled by diffusion and was close to 100% efficiency, as long as biofilm accumulated on the polyester-fiber surface and the fibers had no leaks.     

Combustion Characteristics of Spent Catalyst and Paper Sludge in an Internally Circulating Fluidized-Bed Combustor

Abstract

Combustion of spent vacuum residue hydrodesulfurization catalyst and incineration of paper sludge were carried out in thermo-gravimetric analyzer and an internally circulating fluidized-bed (ICFB) reactor. From the thermogravimetric analyzer-differential thermo-gravimetric curves, the pre-exponential factors and activation energies are determined at the divided temperature regions, and the thermo-gravimetric analysis patterns can be predicted by the kinetic equations. The effects of bed temperature, gas velocity in the draft tube and annulus, solid circulation rate, and waste feed rate on combustion efficiency of the wastes have been determined in an ICFB from the experiments and the model studies. The ICFB combustor exhibits uniform temperature distribution along the bed height with high combustion efficiency (>90%). The combustion efficiency increases with increasing reaction temperature, gas velocity in the annulus region, and solid circulation rate and decreases with increasing waste feed rate and gas velocity in the draft tube. The simulated data from the kinetic equation and the hydrodynamic models predict the experimental data reasonably well.     

Chemical characteristics of fine particulate matters measured during severe winter haze events in Ulaanbaatar,Mongolia

In order to investigate the chemical characteristics of atmospheric aerosol measured during a severe winter haze event, 12-hr PM_2.5 (particulate matter with an aerodynamic diameter ≤2.5 μm) samples were collected at an urban site in Ulaanbaatar, Mongolia, from January 9 to February 17, 2008. On average, 12-hr PM_2.5 mass concentration was 105.1 ± 34.9 μg/m³. Low PM_2.5 mass concentrations were measured when low pressure developed over central Mongolia. The 12-hr average organic mass by carbon (OMC) varied from 6.4 to 132.3 μg/m³, with a mean of 54.9 ± 25.4 μg/m³, whereas elemental carbon (EC) concentration ranged from 0.1 to 3.6 μgC/m³, with a mean of 1.5 ± 0.8 μgC/m³. Ammonium sulfate was found to be the most abundant water-soluble ionic component in Ulaanbaatar during the sampling period, with an average concentration of 11.3 ± 5.0 μg/m³. In order to characterize the effect of air mass pathway on fine particulate matter characteristics, 5-day back-trajectory analysis was conducted, using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. The haze level was classified into three categories, based on the 5-day air mass back trajectories, as Stagnant (ST), Continental (CT), and Low Pressure (LP) cases. PM_2.5 mass concentration during the Stagnant condition was approximately 2.5 times higher than that during the Low Pressure condition, mainly due to increased pollutant concentration of OMC and secondary ammonium sulfate.

Implications: Mongolia is experiencing rapid rates of urbanization similar to other Asian countries, resulting in air pollution problems by the growing number of automobiles and industrialization. Ulaanbaatar, capital of Mongolia, is inherently vulnerable to air pollution because of its emission sources, topography, and meteorological characteristics. Very limited measurements on chemical characteristics of particulate matter have been carried out in Ulaanbaatar, Mongolia.     

Thermodynamic behavior of rare metals in the melting process of municipal solid waste (MSW) incineration residues

This study aims to identify the thermodynamic behavior of rare metal elements during the melting process of municipal solid waste incineration residues. The fate of several selected rare metal elements was investigated using two approaches: experimental and thermodynamic equilibrium calculation at two actual melting plants. The results revealed that Ag, Bi, Ga, Ge, In, Pd, Sb, Te, and Tl are readily volatilized as chloride and/or gaseous forms and then condensed in melting furnace fly ash. On the other hand, Cr, Ni, Ta, V, and Zr tend to mostly remain in molten slag. Sn is volatilized as SnS (g) under reducing conditions while volatilization is suppressed under oxidizing conditions. Thermodynamically, total volatilization of Mn as MnCl2 (g) occurred with highly available chlorine under oxidizing conditions. However, at the actual plants, only a small proportion was volatilized. As for Co, Mo, and W, no volatilization occurred at the actual plants although the calculations suggest that these elements can form volatile metal chloride and volatilize. Non-equilibrium and heterogeneity of the actual plant melting furnace could explain the discrepancy. This study provided a good qualitative view of the behavior of rare metals in the melting process, but further investigation is required to produce a more accurate simulation and to resolve the discrepancy.     

The environmental impact of industrialization in East Asia and strategies toward sustainable development

The East Asian economy has been growing fast in recent years, and environmental stresses are building up rapidly. Transboundary air pollution, water shortages, drinking water contamination, freshwater and marine pollution, deforestation, climatic disasters, and other environmental problems are becoming serious threats to the well-being of people in this densely populated region. The ESI (environmental sustainability index) reported by the World Economic Forum in 2005 is a good indicator of the environmental status of the region; most East Asian countries ranked at the bottom. East Asia is not moving toward a sustainable society, and the environment will not sustain the current rate of economic development for long. The traditional culture of East Asia used to be sustainable, so we can learn much from our traditions. Land use should be planned from an ecological point of view so as to best preserve the land’s productivity and stability. There should be definite goals as to where and how much to preserve the three important ecological bases: forests, coastal wetlands and agricultural farms. The forest is the base for the terrestrial ecosystem, including flood control, water resources, and climate; the coastal wetland is the base for the marine ecosystem; farmland is the base for producing food. Within these defined goals, limits should be set on how much land can be utilized for activities like urban development, manufacturing, and recreation. Limits on the pollution load resulting from such activities should be set so as not to irreversibly damage the environment. Economic development should be planned to allow the use of energy and resources only after satisfying these constraints.

Accelerating preliminary eco-innovation design for products that integrates case-based reasoning and TRIZ method

While the innovativeness and market potential of a new product is normally emphasized, its environmental impact is often neglected. Despite their ability to help designers reduce the environmental impact of products throughout their life cycle, many eco-design methods focus on the redesign of existing products, necessitating a more innovative design capacity. This work describes a novel model to accelerate the preliminary eco-innovation product design by integrating the advantages of case-based reasoning and the TRIZ method. Previous cases from a database support a novel design to satisfy functional performances under the CBR framework. The innovative principles and evolution patterns of the TRIZ method can enhance the design level of new products to achieve eco-innovation. Four eco-innovation concepts for a PC mouse demonstrate the effectiveness of the proposed model.