Studies on the relationship between moisture behavior and gaseous VOCs （Volatile Organic Compounds） removal efficiency of packed tower biofilters are limited. In this research, the nutrient holding capacity, moist...Studies on the relationship between moisture behavior and gaseous VOCs （Volatile Organic Compounds） removal efficiency of packed tower biofilters are limited. In this research, the nutrient holding capacity, moisture evaporation rate and gaseous toluene and MEK （Methyl Ethyl Ketone） removal efficiencies of bioreactors with porous synthetic resin as the packing material were simultaneously observed. The nutrient holding capacity in one of the reactors was higher than those of the other two because its packing layer was frequently supplied with a nutrient solution by soaking. This reactor exhibited the highest toluene removal efficiency. However, excessive biomass growth was observed in this reactor. The reactor with a less frequent supply of nutrient solution by soaking showed a slightly lower toluene removal efficiency, possibly due to lack of nutrients in the packing layer. The reactor that was fed with the nutrient solution by spraying it onto the packing layer （a common method for supplying moisture） had the lowest toluene removal efficiency, mainly because of the uneven distribution of nutrients. Moreover, the moisture evaporation rate in the packing layer during moisture supply and heat balance were determined.展开更多
Volatile organic compounds （VOCs） are widely used in various industrial processes and generate water pollutions. VOCs removal from raw water is an important task for waterworks to guarantee drinking water security. ...Volatile organic compounds （VOCs） are widely used in various industrial processes and generate water pollutions. VOCs removal from raw water is an important task for waterworks to guarantee drinking water security. The removal of VOCs such as chlorobenzene （CB） and ethylbenzene （EB） from raw water by air stripping was investigated under various conditions, inciuding the variation of temperature （5-30~C）, pH （3.5-10.5）, and air/water ratio （10-60）. The air stripping removal efficiency of VOCs decreased with VOCs concentration declining in water. And Henry＇s law constant was demonstrated as an indicator of the estimation of VOCs removal efficiency for air stripping. The effects of temperature and the ratio of air and water were found to play a great role in VOCs removal, but the effect of pH seemed to be negligible. This study demonstrates that air stripping provides a promising opportunity in removing VOCs in drinking water treatment, especially for the relatively high concentration of VOCs.展开更多
Population exposure to pollutants is important for studies on the exposure-response relationship. However, it is difficult to evaluate population exposure to non-conventional pollutants due to limited data on concentr...Population exposure to pollutants is important for studies on the exposure-response relationship. However, it is difficult to evaluate population exposure to non-conventional pollutants due to limited data on concentration levels and the movement patterns of inhabitants. In this study, an air dispersion model was used to simulate N, N-dimethylformarnide （DMF） concentrations, as a proxy to monitoring concentrations. A total of 1289 randomly selected household representatives were surveyed to obtain information on movement characteristics. Subsequently, population movement patterns were combined with DMF concentration levels on maps of 100 m× 100 m resolution to calculate population exposure. During 2008, the estimated population exposure to DMF ranged from 0.002 to 0.64 mg/m^3. The highest level of population exposure to DMF was found in the north and northwest sub-districts of the study area, ranging from 0.42 to 0.64 mg/m^3. The population exposure to DMF for different occupational groups indicated that retired people and farmers were vulnerable subpopulations among people highly exposed to DME This was mainly because they spent most time at home where the DMF concentration was high. As pollutant concentrations were divided into small grids, we found that exposure levels were substantially impacted by population movement characteristics.展开更多
文摘Studies on the relationship between moisture behavior and gaseous VOCs （Volatile Organic Compounds） removal efficiency of packed tower biofilters are limited. In this research, the nutrient holding capacity, moisture evaporation rate and gaseous toluene and MEK （Methyl Ethyl Ketone） removal efficiencies of bioreactors with porous synthetic resin as the packing material were simultaneously observed. The nutrient holding capacity in one of the reactors was higher than those of the other two because its packing layer was frequently supplied with a nutrient solution by soaking. This reactor exhibited the highest toluene removal efficiency. However, excessive biomass growth was observed in this reactor. The reactor with a less frequent supply of nutrient solution by soaking showed a slightly lower toluene removal efficiency, possibly due to lack of nutrients in the packing layer. The reactor that was fed with the nutrient solution by spraying it onto the packing layer （a common method for supplying moisture） had the lowest toluene removal efficiency, mainly because of the uneven distribution of nutrients. Moreover, the moisture evaporation rate in the packing layer during moisture supply and heat balance were determined.
基金National High Technology Research and Development Program of China(863 program)(No.2008AA06A414)Major Science and Technology Proyran for Water Pollution Control and Treatment,China(No.2008ZX07421-003)
文摘Volatile organic compounds （VOCs） are widely used in various industrial processes and generate water pollutions. VOCs removal from raw water is an important task for waterworks to guarantee drinking water security. The removal of VOCs such as chlorobenzene （CB） and ethylbenzene （EB） from raw water by air stripping was investigated under various conditions, inciuding the variation of temperature （5-30~C）, pH （3.5-10.5）, and air/water ratio （10-60）. The air stripping removal efficiency of VOCs decreased with VOCs concentration declining in water. And Henry＇s law constant was demonstrated as an indicator of the estimation of VOCs removal efficiency for air stripping. The effects of temperature and the ratio of air and water were found to play a great role in VOCs removal, but the effect of pH seemed to be negligible. This study demonstrates that air stripping provides a promising opportunity in removing VOCs in drinking water treatment, especially for the relatively high concentration of VOCs.
基金Project (No. 200809103) supported by the State Environmental Protection Commonweal Trade Scientific Research of Ministry of Environmental Protection of China
文摘Population exposure to pollutants is important for studies on the exposure-response relationship. However, it is difficult to evaluate population exposure to non-conventional pollutants due to limited data on concentration levels and the movement patterns of inhabitants. In this study, an air dispersion model was used to simulate N, N-dimethylformarnide （DMF） concentrations, as a proxy to monitoring concentrations. A total of 1289 randomly selected household representatives were surveyed to obtain information on movement characteristics. Subsequently, population movement patterns were combined with DMF concentration levels on maps of 100 m× 100 m resolution to calculate population exposure. During 2008, the estimated population exposure to DMF ranged from 0.002 to 0.64 mg/m^3. The highest level of population exposure to DMF was found in the north and northwest sub-districts of the study area, ranging from 0.42 to 0.64 mg/m^3. The population exposure to DMF for different occupational groups indicated that retired people and farmers were vulnerable subpopulations among people highly exposed to DME This was mainly because they spent most time at home where the DMF concentration was high. As pollutant concentrations were divided into small grids, we found that exposure levels were substantially impacted by population movement characteristics.
