No abstract

No abstract

Monoaromatic pollutants such as benzene, toluene, ethylbenzene and mixture of xylenes are now considered as widespread contaminants of groundwater. In situ bioremediation under natural attenuation or enhanced remediation has been successfully used for removal of organic pollutants, including monoaromatic compounds, from groundwater. Results published indicate that in some sites, intrinsic bioremediation can reduce the monoaromatic compounds content of contaminated water to reach standard levels of potable water. However, engineering bioremediation is faster and more efficient. Also, studies have shown that enhanced anaerobic bioremediation can be applied for many BTEX contaminated groundwaters, as it is simple, applicable and economical. This paper reviews microbiology and metabolism of monoaromatic biodegradation and in situ bioremediation for BTEX removal from groundwater under aerobic and anaerobic conditions. It also discusses the factors affecting and limiting bioremediation processes and interactions between monoaromatic pollutants and other compounds during the remediation processes.

Monoaromatic pollutants such as benzene, toluene, ethylbenzene and mixture of xylenes are now considered as widespread contaminants of groundwater. In situ bioremediation under natural attenuation or enhanced remediation has been successfully used for removal of organic pollutants, including monoaromatic compounds, from groundwater. Results published indicate that in some sites, intrinsic bioremediation can reduce the monoaromatic compounds content of contaminated water to reach standard levels of potable water. However, engineering bioremediation is faster and more efficient. Also, studies have shown that enhanced anaerobic bioremediation can be applied for many BTEX contaminated groundwaters, as it is simple, applicable and economical. This paper reviews microbiology and metabolism of monoaromatic biodegradation and in situ bioremediation for BTEX removal from groundwater under aerobic and anaerobic conditions. It also discusses the factors affecting and limiting bioremediation processes and interactions between monoaromatic pollutants and other compounds during the remediation processes.

Fuel cells are under development for a range of applications for transport, stationary and portable power appliances. Fuel cell technology has advanced to the stage where commercial field trials for both transport and stationary applications are in progress. Direct Carbon Fuel Cells (DCFC) utilize solid carbon as the fuel and have historically attracted less investment than other types of gas or liquid fed fuel cells. However, volatility in gas and oil commodity prices and the increasing concern about the environmental impact of burning heavy fossil fuels for power generation has led to DCFCs gaining more attention within the global study community. A DCFC converts the chemical energy in solid carbon directly into electricity through its direct electrochemical oxidation. The fuel utilization can be almost 100% as the fuel feed and product gases are distinct phases and thus can be easily separated. This is not the case with other fuel cell types for which the fuel utilization within the cell is typically limited to below 85%. The theoretical efficiency is also high, around 100%. The combination of these two factors, lead to the projected electric efficiency of DCFC approaching 80% - approximately twice the efficiency of current generation coal fired power plants, thus leading to a 50% reduction in greenhouse gas emissions. The amount of CO2 for storage/sequestration is also halved. Moreover, the exit gas is an almost pure CO2 stream, requiring little or no gas separation before compression for sequestration. Therefore, the energy and cost penalties to capture the CO2 will also be significantly less than for other technologies. Furthermore, a variety of abundant fuels such as coal, coke, tar, biomass and organic waste can be used. Despite these advantages, the technology is at an early stage of development requiring solutions to many complex challenges related to materials degradation, fuel delivery, reaction kinetics, stack fabrication and system design, before it can be considered for commercialization. This paper, following a brief introduction to other fuel cells, reviews in detail the current status of the direct carbon fuel cell technology, recent progress, technical challenges and discusses the future of the technology.