This study evaluated the capability of a constructed wetland for treating saline wastewater. A pilot-scale constructed wetland system was set up and was initially operated at low, then increasing salt levels to determ...This study evaluated the capability of a constructed wetland for treating saline wastewater. A pilot-scale constructed wetland system was set up and was initially operated at low, then increasing salt levels to determine the effect of salinity on the contaminants＇ removal performance. The effect of hydraulic retention time （HRT） variation on treatment efficiency of the reed wetland was also discussed. Average removal efficiencies of the reed （Phragmites australis） wetland were found to be 79.0% for COD, 72.2% for ammonia nitrogen （NH3-N） and 82.8% for total phosphorus （TP）. Reed planting had obvious improvement on COD and NH3-N removal efficiency when compared to an unplanted system. With the seawater proportion in the influent increasing from 20% to 30%, the TP removal efficiency improved obviously. COD removal efficiency of the reed wetland was positively correlated with HRT under high salinity condition, while excess HRT had adverse impacts on the NH3-N and TP removal. Optimal HRT for NH3-N and TP removal was 4 days. Results obtained can be beneficially used to improve the use of constructed wetlands in saline wastewater treatment.展开更多
Constructed rhizofiltration is a relatively new technology and has potential in agricultural wastewater treatment. It has been reported to reduce heavy metals in wastewater but no substantive work has been reported ab...Constructed rhizofiltration is a relatively new technology and has potential in agricultural wastewater treatment. It has been reported to reduce heavy metals in wastewater but no substantive work has been reported about its ability to remove nitrogen and phosphorus, particularly in agricultural wastewater. If this technology＇s worth in nutrient removal from wastewater can be proved, it can save time as well as reducing wastewater treatment cost. Influent and effluent nitrogen and phosphate concentrations in the constructed rhizofiltration were measured and it was found that there was a significant difference between the two water samples （P = 0.01）. It was also found that more nitrogen and phosphate were retained by planted region （P = 0.01） compared to unplanted （P = 0.02）, demonstrating high removal efficiency in the planted region than in the unplanted region. Eighty six percent （86%） removal efficiency of phosphorus was achieved at some points in the planted region while 71% was achieved for nitrogen. These results indicate that constructed rhizofiltration systems, if properly constructed and planted with macrophytes and maintained, can be used for nitrogen and phosphorus removal in wastewater and thus could be used as an alternative technology for agricultural wastewater treatment.展开更多
The growth of reeds was impeded remarkably under a salinity of 15.0±3.4 g CI·L-1 in the first year of this experiment, recovered in the second year and then increased year-by-year afterward. The growth of re...The growth of reeds was impeded remarkably under a salinity of 15.0±3.4 g CI·L-1 in the first year of this experiment, recovered in the second year and then increased year-by-year afterward. The growth of reeds under a salinity of 9.3±1.9 g CI·Ll was much better than those under 15.0 ± 3.4 g CI·L1. The stress effect was significant for shoot extension but not for the quantity of shoots increase. The dense vegetation bed during the vegetation period （June-October） provided a high rate of evapotranspiration and water loss from HFs （horizontal subsurface flow constructed wetlands）, which made large contributions to reducing pollutant load. The HFs with die-back reeds in the non-vegetation periods （November-March） provided slight evapotranspiration and water loss and made less of a contribution to reducing pollutants removal compared to HFs with the dense vegetation bed in the vegetation periods. However, the HFs with die-back reeds in the non-vegetation periods had higher removal performance than the HF without reeds. This indicated that the rhizosphere of HFs with reeds might play important roles, such as that the microbes around rhizomes might have a higher amount of pollutant-removing microbe activity than those in the HF without reeds during the non-vegetation period.展开更多
In this study, the water budget in the treatment of high salinity landfill-leachate was estimated and the influence of evapotranspiration （ET） on treatment performance was investigated. The salinity of the inside of...In this study, the water budget in the treatment of high salinity landfill-leachate was estimated and the influence of evapotranspiration （ET） on treatment performance was investigated. The salinity of the inside of horizontal subsurface flow constructed wetland （HSF） of the raw leachate inflow was 15.0± 3.4 g.Cl/L which was in the level of the salinity of the survival limit of reed, and that of the double diluted leachate inflow was 9.3 ± 1.9 g.CI7L. There were large differences in the vegetation between HSF of the raw leachate inflow and that of the double diluted leachate inflow. The dense vegetation bed of double diluted leachate inflow during the growing season （April-October） provided a high ET and a large water loss, which made great contributions to the reduction of the outflow load of COD and T-N. The HSF with die-back reeds in the non-growing season （November-March） provided a slight ET and a small water loss and made less of a contribution to pollutant removal compared to the HSF with dense vegetation bed during the growing season. However, the HSF with die-back reeds during the non-growing season exhibited higher removal performance than the unplanted HSF.展开更多
文摘This study evaluated the capability of a constructed wetland for treating saline wastewater. A pilot-scale constructed wetland system was set up and was initially operated at low, then increasing salt levels to determine the effect of salinity on the contaminants＇ removal performance. The effect of hydraulic retention time （HRT） variation on treatment efficiency of the reed wetland was also discussed. Average removal efficiencies of the reed （Phragmites australis） wetland were found to be 79.0% for COD, 72.2% for ammonia nitrogen （NH3-N） and 82.8% for total phosphorus （TP）. Reed planting had obvious improvement on COD and NH3-N removal efficiency when compared to an unplanted system. With the seawater proportion in the influent increasing from 20% to 30%, the TP removal efficiency improved obviously. COD removal efficiency of the reed wetland was positively correlated with HRT under high salinity condition, while excess HRT had adverse impacts on the NH3-N and TP removal. Optimal HRT for NH3-N and TP removal was 4 days. Results obtained can be beneficially used to improve the use of constructed wetlands in saline wastewater treatment.
文摘Constructed rhizofiltration is a relatively new technology and has potential in agricultural wastewater treatment. It has been reported to reduce heavy metals in wastewater but no substantive work has been reported about its ability to remove nitrogen and phosphorus, particularly in agricultural wastewater. If this technology＇s worth in nutrient removal from wastewater can be proved, it can save time as well as reducing wastewater treatment cost. Influent and effluent nitrogen and phosphate concentrations in the constructed rhizofiltration were measured and it was found that there was a significant difference between the two water samples （P = 0.01）. It was also found that more nitrogen and phosphate were retained by planted region （P = 0.01） compared to unplanted （P = 0.02）, demonstrating high removal efficiency in the planted region than in the unplanted region. Eighty six percent （86%） removal efficiency of phosphorus was achieved at some points in the planted region while 71% was achieved for nitrogen. These results indicate that constructed rhizofiltration systems, if properly constructed and planted with macrophytes and maintained, can be used for nitrogen and phosphorus removal in wastewater and thus could be used as an alternative technology for agricultural wastewater treatment.
文摘The growth of reeds was impeded remarkably under a salinity of 15.0±3.4 g CI·L-1 in the first year of this experiment, recovered in the second year and then increased year-by-year afterward. The growth of reeds under a salinity of 9.3±1.9 g CI·Ll was much better than those under 15.0 ± 3.4 g CI·L1. The stress effect was significant for shoot extension but not for the quantity of shoots increase. The dense vegetation bed during the vegetation period （June-October） provided a high rate of evapotranspiration and water loss from HFs （horizontal subsurface flow constructed wetlands）, which made large contributions to reducing pollutant load. The HFs with die-back reeds in the non-vegetation periods （November-March） provided slight evapotranspiration and water loss and made less of a contribution to reducing pollutants removal compared to HFs with the dense vegetation bed in the vegetation periods. However, the HFs with die-back reeds in the non-vegetation periods had higher removal performance than the HF without reeds. This indicated that the rhizosphere of HFs with reeds might play important roles, such as that the microbes around rhizomes might have a higher amount of pollutant-removing microbe activity than those in the HF without reeds during the non-vegetation period.
文摘In this study, the water budget in the treatment of high salinity landfill-leachate was estimated and the influence of evapotranspiration （ET） on treatment performance was investigated. The salinity of the inside of horizontal subsurface flow constructed wetland （HSF） of the raw leachate inflow was 15.0± 3.4 g.Cl/L which was in the level of the salinity of the survival limit of reed, and that of the double diluted leachate inflow was 9.3 ± 1.9 g.CI7L. There were large differences in the vegetation between HSF of the raw leachate inflow and that of the double diluted leachate inflow. The dense vegetation bed of double diluted leachate inflow during the growing season （April-October） provided a high ET and a large water loss, which made great contributions to the reduction of the outflow load of COD and T-N. The HSF with die-back reeds in the non-growing season （November-March） provided a slight ET and a small water loss and made less of a contribution to pollutant removal compared to the HSF with dense vegetation bed during the growing season. However, the HSF with die-back reeds during the non-growing season exhibited higher removal performance than the unplanted HSF.
