语料库用于外语教学和研究已被广泛探讨。但国内德语学习者普遍对德语语料库了解不多,难以主动且系统地使用语料库辅助德语学习。德语电子辞典(全称Das Digitale Wörterbuch der deutschen Sprache,网页:www.dwds.de)是权威且重要...语料库用于外语教学和研究已被广泛探讨。但国内德语学习者普遍对德语语料库了解不多,难以主动且系统地使用语料库辅助德语学习。德语电子辞典(全称Das Digitale Wörterbuch der deutschen Sprache,网页:www.dwds.de)是权威且重要的德语学习资源,该文详细介绍DWDS的结构和功能,并以实例探讨如何用其辅助不同阶段的德语词汇学习,以期为广大德语学习者提供示例。展开更多
Nitrite in drinking water is a potential health hazard and monitoring its concentrations in distributed water is of paramount importance. When monochloramine is used in secondary disinfection in drinking water distrib...Nitrite in drinking water is a potential health hazard and monitoring its concentrations in distributed water is of paramount importance. When monochloramine is used in secondary disinfection in drinking water distribution systems (DWDSs), nitrite is often formed by nitrification in the biofilm on the inner surface of distribution pipes. This article attempts to identify areas with a risk of increased nitrite concentrations as well as the main reasons leading to nitrite occurrence in a large urban DWDS in Finland using spatial inspection of obligatory monitoring data. Nitrification was found to occur throughout the study area, though nitrite was not increased everywhere. Instead, nitrite was increased close to the water treatment plants (WTPs) and was connected to fresh drinking water than stagnant drinking water. Temperature effects on nitrite concentrations were surprisingly insignificant, even though it is well known that nitrification reactions are affected by temperature. The temperature dependence of ammonium and total residual chlorine was more significant than the dependence of nitrite. The findings of this study emphasize the need to monitor nitrite concentrations close to WTPs.展开更多
Within the drinking water distribution system(DWDS)using chloramine as disinfectant,nitrification caused by nitrifying bacteria is increasingly becoming a concern as it poses a great challenge for maintaining water qu...Within the drinking water distribution system(DWDS)using chloramine as disinfectant,nitrification caused by nitrifying bacteria is increasingly becoming a concern as it poses a great challenge for maintaining water quality.To investigate efficient control strategies,operational conditions including hydraulic regimes and disinfectant scenarios were controlled within a flow cell experimental facility.Two test phases were conducted to investigate the effects on the extent of nitrification of three flow rates(Q=2,6,and 10 L/min)and four disinfection scenarios(total Cl2=1 mg/L,Cl2/NH3-N=3:1;total Cl2=1 mg/L,Cl2/NH3-N=5:1;total Cl2=5 mg/L,Cl2/NH3-N=3:1;and total Cl2=5 mg/L,Cl2/NH3-N=5:1).Physico-chemical parameters and nitrification indicators were monitored during the tests.The characteristics of biofilm extracellular polymetric substance(EPS)were evaluated after the experiment.The main results from the study indicate that nitrification is affected by hydraulic conditions and the process tends to be severe when the fluid flow transforms from laminar to turbulent(2300<Re<4000).Increasing disinfectant concentration and optimizing Cl2/NH3-N mass ratio were found to inhibit nitrification to some extend when the system was running at turbulent condition(Q=10 L/min,Re=5535).EPS extracted from biofilm that was established at the flow rate of 6 L/min had greater carbohydrate/protein ratio.Furthermore,several nitrification indicators were evaluated for their prediction efficiency and the results suggest that the change of nitrite,together with total organic carbon(TOC)and turbidity can indicate nitrification potential efficiently.展开更多
文摘语料库用于外语教学和研究已被广泛探讨。但国内德语学习者普遍对德语语料库了解不多,难以主动且系统地使用语料库辅助德语学习。德语电子辞典(全称Das Digitale Wörterbuch der deutschen Sprache,网页:www.dwds.de)是权威且重要的德语学习资源,该文详细介绍DWDS的结构和功能,并以实例探讨如何用其辅助不同阶段的德语词汇学习,以期为广大德语学习者提供示例。
基金foundation of Maa-ja vesitekniikan tuki ry.,for financing the research.
文摘Nitrite in drinking water is a potential health hazard and monitoring its concentrations in distributed water is of paramount importance. When monochloramine is used in secondary disinfection in drinking water distribution systems (DWDSs), nitrite is often formed by nitrification in the biofilm on the inner surface of distribution pipes. This article attempts to identify areas with a risk of increased nitrite concentrations as well as the main reasons leading to nitrite occurrence in a large urban DWDS in Finland using spatial inspection of obligatory monitoring data. Nitrification was found to occur throughout the study area, though nitrite was not increased everywhere. Instead, nitrite was increased close to the water treatment plants (WTPs) and was connected to fresh drinking water than stagnant drinking water. Temperature effects on nitrite concentrations were surprisingly insignificant, even though it is well known that nitrification reactions are affected by temperature. The temperature dependence of ammonium and total residual chlorine was more significant than the dependence of nitrite. The findings of this study emphasize the need to monitor nitrite concentrations close to WTPs.
基金support from the technicians at the School of Engineering,Cardiff University。
文摘Within the drinking water distribution system(DWDS)using chloramine as disinfectant,nitrification caused by nitrifying bacteria is increasingly becoming a concern as it poses a great challenge for maintaining water quality.To investigate efficient control strategies,operational conditions including hydraulic regimes and disinfectant scenarios were controlled within a flow cell experimental facility.Two test phases were conducted to investigate the effects on the extent of nitrification of three flow rates(Q=2,6,and 10 L/min)and four disinfection scenarios(total Cl2=1 mg/L,Cl2/NH3-N=3:1;total Cl2=1 mg/L,Cl2/NH3-N=5:1;total Cl2=5 mg/L,Cl2/NH3-N=3:1;and total Cl2=5 mg/L,Cl2/NH3-N=5:1).Physico-chemical parameters and nitrification indicators were monitored during the tests.The characteristics of biofilm extracellular polymetric substance(EPS)were evaluated after the experiment.The main results from the study indicate that nitrification is affected by hydraulic conditions and the process tends to be severe when the fluid flow transforms from laminar to turbulent(2300<Re<4000).Increasing disinfectant concentration and optimizing Cl2/NH3-N mass ratio were found to inhibit nitrification to some extend when the system was running at turbulent condition(Q=10 L/min,Re=5535).EPS extracted from biofilm that was established at the flow rate of 6 L/min had greater carbohydrate/protein ratio.Furthermore,several nitrification indicators were evaluated for their prediction efficiency and the results suggest that the change of nitrite,together with total organic carbon(TOC)and turbidity can indicate nitrification potential efficiently.
