To investigate the characteristics of disinfection by-products （DBPs） in an actual water distribution system using the raw water with high bromide ion concentration, the composition and concentration of trihalometha...To investigate the characteristics of disinfection by-products （DBPs） in an actual water distribution system using the raw water with high bromide ion concentration, the composition and concentration of trihalomethanes （THMs） formed by chlorination of the water in the presence of bromide ion were measured in a city water distribution system during one year. The results show that brominated THMs contributed a great part （83%-89% ） to the index for additive toxicity （ATI） and resulted in the ATI of most of the samples exceeding WHO guideline standard for total THMs （ TTHMs）, especially during the summer （ rainy season）. This indicates that the chlorination of water in the presence of bromide ion leaded to high ratios of brominated THMs to TrHMs. However, a visible increase in the concentration of THMs with increasing residence time in the distribution system was not observed. Additionally, based on alternatives analysis, packed tower aeration method is proposed to reduce THMs level of the finished water leaving the treatment plant.展开更多
In this paper we give six explicit formulae to compute the Kirchhoff index,the multiplicative degree-Kirchhoff index and the additive degree-Kirchhoff index of the k-cactus chain and the cactus graph which can be obta...In this paper we give six explicit formulae to compute the Kirchhoff index,the multiplicative degree-Kirchhoff index and the additive degree-Kirchhoff index of the k-cactus chain and the cactus graph which can be obtained from a k-cactus chain by expanding each of the cut-vertices to a cut edge.展开更多
基金National High-Tech Research and Development Program of China ( 863 Program ) ( No.2007AA06Z303)
文摘To investigate the characteristics of disinfection by-products （DBPs） in an actual water distribution system using the raw water with high bromide ion concentration, the composition and concentration of trihalomethanes （THMs） formed by chlorination of the water in the presence of bromide ion were measured in a city water distribution system during one year. The results show that brominated THMs contributed a great part （83%-89% ） to the index for additive toxicity （ATI） and resulted in the ATI of most of the samples exceeding WHO guideline standard for total THMs （ TTHMs）, especially during the summer （ rainy season）. This indicates that the chlorination of water in the presence of bromide ion leaded to high ratios of brominated THMs to TrHMs. However, a visible increase in the concentration of THMs with increasing residence time in the distribution system was not observed. Additionally, based on alternatives analysis, packed tower aeration method is proposed to reduce THMs level of the finished water leaving the treatment plant.
基金Supported by the National Natural Science Foundations of China(No.11401102)
文摘In this paper we give six explicit formulae to compute the Kirchhoff index,the multiplicative degree-Kirchhoff index and the additive degree-Kirchhoff index of the k-cactus chain and the cactus graph which can be obtained from a k-cactus chain by expanding each of the cut-vertices to a cut edge.
