The pollution caused by wet weather overflow in urban drainage systems is a main factor causing blackening an odorization of urban rivers.The conventional overflow treatment based on coagulation/flocculation in termin...The pollution caused by wet weather overflow in urban drainage systems is a main factor causing blackening an odorization of urban rivers.The conventional overflow treatment based on coagulation/flocculation in terminal drainage systems requires relatively large space and long retention time demand that makes it not applicable in crowded urban drainage systems or under heavy rains.On-site coagulation/flocculation in terminal drainage pipes was proposed in this study which was aimed to transfer the coagulation/flocculation process to the inside of pipes at the terminal drainage system to save space and reduce the retention time of the coagulation/flocculation process.The optimized dose of chemicals was studied first which was 80 mg/L of coagulant and 0.8 mg/L of flocculant.Settling for only 5 min can remove most of the pollutants at 406.5 m of transmission distance.In addition,the relation of wet weather overflow rate and concentration of pollution load on the on-site coagulation/flocculation process was investigated,which indicated that high removal of pollutant was gained at a large range of flow velocity and pollutant concentration.Finally,the study confirmed electric neutralization,bridging,and net capture as the major mechanisms in this process,and further optimization was proposed.The proposed process can reduce much turbidity,chemical oxygen demand,and total phosphorous,but hardly remove soluble ammonia and organics.This work provides scientific guidance to address wet weather overflow in terminal drainage pipes.展开更多
Two types of pisha-sandstones of purple sandstones and gray sandstones,widely distributing in the wind-water erosion crisscross region of China,were selected and used in laboratory experiments for a better understandi...Two types of pisha-sandstones of purple sandstones and gray sandstones,widely distributing in the wind-water erosion crisscross region of China,were selected and used in laboratory experiments for a better understanding of the drying-wetting-freezing weathering process resulting from the apportionment of water or salt solution to rock samples.Weathering experiments were carried out under the conditions of environment control(including temperature,moisture and salt solution).All rock samples were frequently subjected to 140 drying-wetting-freezing cycles.The influences of weathering process were evaluated.It was found that the different treatments of moisture and salt solution applications could affect the nature of the weathering products resulting from drying-wetting-freezing.It was also observed that salt solution could effectively alleviate the weathering of pisha-sandstones.Although not all the observations could be explained,it was apparent that simulated environmental factors had both direct and indirect effects on the weathering of rocks.展开更多
Heavy rain is a common abnormal weather in China, which is prone to major natural disasters such as floods. By using China National Climate Center’s DERF2.0 (the second-generation product of monthly dynamic extended ...Heavy rain is a common abnormal weather in China, which is prone to major natural disasters such as floods. By using China National Climate Center’s DERF2.0 (the second-generation product of monthly dynamic extended ensemble prediction) models and NCEP (National Centers for Environmental Prediction) data, and using synoptic and dynamic methods and other research methods, the rainfall weather process in most of China from October 3-6, 2021 is analyzed. The results show that: 1) this process had a long duration, large cumulative rainfall and strong extreme. 2) The warm and wet flow and the cold air intersected in the central and western regions of China and Northeast China, which resulted in a regional rainstorm process within ten days. 3) There was a low-level jet moving from Guizhou and Hunan to the south of Northeast China, bringing a lot of water vapor. To sum up, the rainfall process of this round has a certain relationship with the adjustment of atmospheric circulation.展开更多
文摘The pollution caused by wet weather overflow in urban drainage systems is a main factor causing blackening an odorization of urban rivers.The conventional overflow treatment based on coagulation/flocculation in terminal drainage systems requires relatively large space and long retention time demand that makes it not applicable in crowded urban drainage systems or under heavy rains.On-site coagulation/flocculation in terminal drainage pipes was proposed in this study which was aimed to transfer the coagulation/flocculation process to the inside of pipes at the terminal drainage system to save space and reduce the retention time of the coagulation/flocculation process.The optimized dose of chemicals was studied first which was 80 mg/L of coagulant and 0.8 mg/L of flocculant.Settling for only 5 min can remove most of the pollutants at 406.5 m of transmission distance.In addition,the relation of wet weather overflow rate and concentration of pollution load on the on-site coagulation/flocculation process was investigated,which indicated that high removal of pollutant was gained at a large range of flow velocity and pollutant concentration.Finally,the study confirmed electric neutralization,bridging,and net capture as the major mechanisms in this process,and further optimization was proposed.The proposed process can reduce much turbidity,chemical oxygen demand,and total phosphorous,but hardly remove soluble ammonia and organics.This work provides scientific guidance to address wet weather overflow in terminal drainage pipes.
基金supported by the National Natural Science Foundation of China (No.40271071)the Foundation of State Key Laboratory of Soil Erosion and Dryland Farming on the Less Plateau (No.10501-113 10501-165)
文摘Two types of pisha-sandstones of purple sandstones and gray sandstones,widely distributing in the wind-water erosion crisscross region of China,were selected and used in laboratory experiments for a better understanding of the drying-wetting-freezing weathering process resulting from the apportionment of water or salt solution to rock samples.Weathering experiments were carried out under the conditions of environment control(including temperature,moisture and salt solution).All rock samples were frequently subjected to 140 drying-wetting-freezing cycles.The influences of weathering process were evaluated.It was found that the different treatments of moisture and salt solution applications could affect the nature of the weathering products resulting from drying-wetting-freezing.It was also observed that salt solution could effectively alleviate the weathering of pisha-sandstones.Although not all the observations could be explained,it was apparent that simulated environmental factors had both direct and indirect effects on the weathering of rocks.
文摘Heavy rain is a common abnormal weather in China, which is prone to major natural disasters such as floods. By using China National Climate Center’s DERF2.0 (the second-generation product of monthly dynamic extended ensemble prediction) models and NCEP (National Centers for Environmental Prediction) data, and using synoptic and dynamic methods and other research methods, the rainfall weather process in most of China from October 3-6, 2021 is analyzed. The results show that: 1) this process had a long duration, large cumulative rainfall and strong extreme. 2) The warm and wet flow and the cold air intersected in the central and western regions of China and Northeast China, which resulted in a regional rainstorm process within ten days. 3) There was a low-level jet moving from Guizhou and Hunan to the south of Northeast China, bringing a lot of water vapor. To sum up, the rainfall process of this round has a certain relationship with the adjustment of atmospheric circulation.
