Fecal indicator bacteria, such as total coliforms and E. coli, are a challenge to control in urban and rural stormwater runoff. To assess the challenges of improving bacterial water quality standards in surface waters...Fecal indicator bacteria, such as total coliforms and E. coli, are a challenge to control in urban and rural stormwater runoff. To assess the challenges of improving bacterial water quality standards in surface waters, microcosm experiments were conducted to assess how decay rates of total coliforms and E. coli are affected by sediments and associated organic matter. Samples were collected at a lake embayment to create laboratory microcosms consisting of different combinations of unsterilized and sterilized water and sediment. Calculated first-order decay rate constants ranged from 0.021 to 0.047 h-1 for total coliforms and 0.017 and 0.037 h-1 for E. coli, depending on how each microcosm was prepared. It is evident that sediment in contact with the water column decreases bacteria decay rate, showing that care should be taken when designing stormwater treatment measures. In addition, high organic carbon content in the sediment temporarily increased bacteria concentrations in the water column. The results demonstrate that stormwater treatment measures, such as extended detention basins and constructed wetlands, must hold water for several days to allow for reduction of bacterial concentrations to acceptable levels. In addition, to troubleshoot detention basins and constructed wetlands for causes of high effluent bacterial concentrations, analyses of sediment, organic carbon, and water column depth should be conducted.展开更多
China is at present experiencing a very rapid urbanization process, which has brought a number of adverse impacts upon the water environment. In particular, urban runoff quantity and quality control have emerged as on...China is at present experiencing a very rapid urbanization process, which has brought a number of adverse impacts upon the water environment. In particular, urban runoff quantity and quality control have emerged as one of the key concerns for municipal officials. One of the strategies being considered is the use of a Low Impact Development type of Best Management Practices （LID BMPs） for urban storm water runoff quantity and quality control. In this paper, the situation surrounding urban runoff control in China is reviewed first. Then the conventional strategy and technologies for the construction and management of urban drainage systems are discussed, while exploring their inherent dilemmas. The LID BMPs are then introduced to control urban runoff in the context of urban sustainable water systems. After the comprehensive analysis of the various LID BMPs, the advances in LID BMPs research and practice for urban runoff control in China are investigated and summarized. At last, the difficulties of implementing LID BMPs in China are discussed, and a direction for the future is proposed.展开更多
Agricultural Best Management Practices （BMPs） are effective ways to reduce agricultural nonpoint source pol ution from their source area to receiving water bodies. Characterization of BMPs in a watershed model is a ...Agricultural Best Management Practices （BMPs） are effective ways to reduce agricultural nonpoint source pol ution from their source area to receiving water bodies. Characterization of BMPs in a watershed model is a critical prerequisite for evaluating their impacts on water quantity and water quality in a complex system. However, limited research has reported about the representation of BMPs in fully distributed models. This paper presents a stepwise procedure for representation of several BMPs and assessment of their hydrologic impacts with a ful y distributed model, SEIM （Spatially Explicit Integrated Modeling）. A case study is conducted in the 73 km2 Luoyugou watershed located in the Loess Plateau of China, where rainstorm erosion accounts for more than 60%of annual sediment load in average. Three BMPs are selected in this study including （i） conversion from farmland to forest, （i ） terrace, and （i i） no-til farming. These management practices are represented in the model through the alteration of model parameters characterizing their physical processes in the ifeld. The results of scenario assessment for a historical storm event showed that the maximum sediment reduction after terrace is about 97.3%, the average sediment reduction after no-till farming is about 9.5%, and the average sediment reduction after conversion from farmland to forest is 75.6%.展开更多
文摘Fecal indicator bacteria, such as total coliforms and E. coli, are a challenge to control in urban and rural stormwater runoff. To assess the challenges of improving bacterial water quality standards in surface waters, microcosm experiments were conducted to assess how decay rates of total coliforms and E. coli are affected by sediments and associated organic matter. Samples were collected at a lake embayment to create laboratory microcosms consisting of different combinations of unsterilized and sterilized water and sediment. Calculated first-order decay rate constants ranged from 0.021 to 0.047 h-1 for total coliforms and 0.017 and 0.037 h-1 for E. coli, depending on how each microcosm was prepared. It is evident that sediment in contact with the water column decreases bacteria decay rate, showing that care should be taken when designing stormwater treatment measures. In addition, high organic carbon content in the sediment temporarily increased bacteria concentrations in the water column. The results demonstrate that stormwater treatment measures, such as extended detention basins and constructed wetlands, must hold water for several days to allow for reduction of bacterial concentrations to acceptable levels. In addition, to troubleshoot detention basins and constructed wetlands for causes of high effluent bacterial concentrations, analyses of sediment, organic carbon, and water column depth should be conducted.
文摘China is at present experiencing a very rapid urbanization process, which has brought a number of adverse impacts upon the water environment. In particular, urban runoff quantity and quality control have emerged as one of the key concerns for municipal officials. One of the strategies being considered is the use of a Low Impact Development type of Best Management Practices （LID BMPs） for urban storm water runoff quantity and quality control. In this paper, the situation surrounding urban runoff control in China is reviewed first. Then the conventional strategy and technologies for the construction and management of urban drainage systems are discussed, while exploring their inherent dilemmas. The LID BMPs are then introduced to control urban runoff in the context of urban sustainable water systems. After the comprehensive analysis of the various LID BMPs, the advances in LID BMPs research and practice for urban runoff control in China are investigated and summarized. At last, the difficulties of implementing LID BMPs in China are discussed, and a direction for the future is proposed.
基金the Major Science and Technology Program for Water Pollution Control and Treatment(No.2013ZX07103006-005)the National Science and Technology Support Program(No.2013BAC08B03-4)
文摘Agricultural Best Management Practices （BMPs） are effective ways to reduce agricultural nonpoint source pol ution from their source area to receiving water bodies. Characterization of BMPs in a watershed model is a critical prerequisite for evaluating their impacts on water quantity and water quality in a complex system. However, limited research has reported about the representation of BMPs in fully distributed models. This paper presents a stepwise procedure for representation of several BMPs and assessment of their hydrologic impacts with a ful y distributed model, SEIM （Spatially Explicit Integrated Modeling）. A case study is conducted in the 73 km2 Luoyugou watershed located in the Loess Plateau of China, where rainstorm erosion accounts for more than 60%of annual sediment load in average. Three BMPs are selected in this study including （i） conversion from farmland to forest, （i ） terrace, and （i i） no-til farming. These management practices are represented in the model through the alteration of model parameters characterizing their physical processes in the ifeld. The results of scenario assessment for a historical storm event showed that the maximum sediment reduction after terrace is about 97.3%, the average sediment reduction after no-till farming is about 9.5%, and the average sediment reduction after conversion from farmland to forest is 75.6%.
