Fluid flow and mixing phenomenon have a significant impact on coagulation and flocculation processes. Particles dissipating the turbulent kinetic energy increase the efficiency of collision, grow in size and incorpora...Fluid flow and mixing phenomenon have a significant impact on coagulation and flocculation processes. Particles dissipating the turbulent kinetic energy increase the efficiency of collision, grow in size and incorporate phosphate from the wastewater Only certain flocks can be separated depending on their stability, size, density, etc.. According to the literature the velocity gradient of the flow （G-value） is the main design parameter of the flocculators, but there is a need to take into account at least the flocks age, too. In this paper, it presents a novel approach to determine the efficiency of flocculators using local mean age theory, residence time distribution and dimensional analysis. Calculations were performed for two constructions of cascade reactors---one with small baffles and one without these; hydraulical performance and the achievable conversion were compared. As a result, the flocculator with small baffles proved to be more efficient than the traditional construction.展开更多
Environmentally persistent free radicals(EPFRs)are a new class of pollutants that are long-lived in fine particles(PM_(2.5)),i.e.,their 1/e lifetime ranges from days to months(or even infinite).They are capable of pro...Environmentally persistent free radicals(EPFRs)are a new class of pollutants that are long-lived in fine particles(PM_(2.5)),i.e.,their 1/e lifetime ranges from days to months(or even infinite).They are capable of producing harmful reactive oxygen species such as hydroxyl radicals.The redox cycling of EPFRs is considered as an important pathway for PM_(2.5) to induce oxidative stress inside the humans,causing adverse health effects such as respiratory and cardiovascular diseases.Conse-quently,research regarding their toxicity,formation and environmental occurrences in PM_(2.5) has attracted increasing atten-tions globally during the past two decades.However,literature data in this field remain quite limited and discrete.Hence,an extensive review is urgently needed to summarize the current understanding of this topic.In this work,we systematically reviewed the analytical methods and environmental occurrences,e.g.,types,concentrations,and decay behaviors,as well as possible sources of EPFRs in PM_(2.5).The types of pretreatment methods,g-values of common EPFRs and categories of decay processes were discussed in detail.Moreover,great efforts were made to revisit the original data of the published works of EPFRs in airborne particulate matter and provided additional useful information for comparison where possible,e.g.,their mean and standard deviation of g-values,line widths(ΔHp-p),and concentrations.Finally,possible research opportunities were highlighted to further advance our knowledge of this emerging issue.展开更多
文摘Fluid flow and mixing phenomenon have a significant impact on coagulation and flocculation processes. Particles dissipating the turbulent kinetic energy increase the efficiency of collision, grow in size and incorporate phosphate from the wastewater Only certain flocks can be separated depending on their stability, size, density, etc.. According to the literature the velocity gradient of the flow （G-value） is the main design parameter of the flocculators, but there is a need to take into account at least the flocks age, too. In this paper, it presents a novel approach to determine the efficiency of flocculators using local mean age theory, residence time distribution and dimensional analysis. Calculations were performed for two constructions of cascade reactors---one with small baffles and one without these; hydraulical performance and the achievable conversion were compared. As a result, the flocculator with small baffles proved to be more efficient than the traditional construction.
基金the Ningbo Natural Science Foundation(Grant no.2018A610208)the National This work was supported by the Ningbo Natural Science Foundation(Grant no.2018A610208)the National Institute of Environmental Health Sciences(NIEHS)(Grant no.2P42ES013648)。
文摘Environmentally persistent free radicals(EPFRs)are a new class of pollutants that are long-lived in fine particles(PM_(2.5)),i.e.,their 1/e lifetime ranges from days to months(or even infinite).They are capable of producing harmful reactive oxygen species such as hydroxyl radicals.The redox cycling of EPFRs is considered as an important pathway for PM_(2.5) to induce oxidative stress inside the humans,causing adverse health effects such as respiratory and cardiovascular diseases.Conse-quently,research regarding their toxicity,formation and environmental occurrences in PM_(2.5) has attracted increasing atten-tions globally during the past two decades.However,literature data in this field remain quite limited and discrete.Hence,an extensive review is urgently needed to summarize the current understanding of this topic.In this work,we systematically reviewed the analytical methods and environmental occurrences,e.g.,types,concentrations,and decay behaviors,as well as possible sources of EPFRs in PM_(2.5).The types of pretreatment methods,g-values of common EPFRs and categories of decay processes were discussed in detail.Moreover,great efforts were made to revisit the original data of the published works of EPFRs in airborne particulate matter and provided additional useful information for comparison where possible,e.g.,their mean and standard deviation of g-values,line widths(ΔHp-p),and concentrations.Finally,possible research opportunities were highlighted to further advance our knowledge of this emerging issue.
