TY - JOUR
T1 - Liquid-gas mass transfer at drop structures
AU - Matias, Natércia
AU - Nielsen, Asbjørn Haaning
AU - Vollertsen, Jes
AU - Ferreira, Filipa
AU - Matos, José Saldanha
PY - 2017
Y1 - 2017
N2 - Over the last decades, considerable progress has been made in the understanding of the sulfur cycle in sewer systems. In spite of a wealth of experimental and field studies that have addressed the release of hydrogen sulfide from free surface flows in gravity sewers and the corresponding air-water mass transfer, little is known about hydrogen sulfide emission under highly turbulent conditions (e.g., drop structures, hydraulic jumps). In this study, experimental work was carried out to analyze the influence of characteristics of drops on reaeration. Physical models were built, mimicking typical sewer drop structures and allowing different types of drops, drop heights, tailwater depths and flow rates. In total, 125 tests were performed. Based on their results, empirical expressions translating the relationship between the mass transfer of oxygen and physical parameters of drop structures were established. Then, by applying the two-film theory with two-reference substances, the relation to hydrogen sulfide release was defined. The experiments confirmed that the choice of the type of drop structure is critical to determine the uptake/emission rates. By quantifying the air-water mass transfer rates between free-fall and backdrop types of drop, the latter resulted in considerably lower oxygen uptake rates.
AB - Over the last decades, considerable progress has been made in the understanding of the sulfur cycle in sewer systems. In spite of a wealth of experimental and field studies that have addressed the release of hydrogen sulfide from free surface flows in gravity sewers and the corresponding air-water mass transfer, little is known about hydrogen sulfide emission under highly turbulent conditions (e.g., drop structures, hydraulic jumps). In this study, experimental work was carried out to analyze the influence of characteristics of drops on reaeration. Physical models were built, mimicking typical sewer drop structures and allowing different types of drops, drop heights, tailwater depths and flow rates. In total, 125 tests were performed. Based on their results, empirical expressions translating the relationship between the mass transfer of oxygen and physical parameters of drop structures were established. Then, by applying the two-film theory with two-reference substances, the relation to hydrogen sulfide release was defined. The experiments confirmed that the choice of the type of drop structure is critical to determine the uptake/emission rates. By quantifying the air-water mass transfer rates between free-fall and backdrop types of drop, the latter resulted in considerably lower oxygen uptake rates.
KW - Air-water mass transfer
KW - Dissolved oxygen
KW - Sewer drop structures
KW - Turbulence
KW - Uptake/emission rates
KW - Air-water mass transfer
KW - Dissolved oxygen
KW - Sewer drop structures
KW - Turbulence
KW - Uptake/emission rates
U2 - 10.2166/wst.2017.103
DO - 10.2166/wst.2017.103
M3 - Journal article
SN - 0273-1223
VL - 75
SP - 2257
EP - 2267
JO - Water Science and Technology
JF - Water Science and Technology
IS - 10
ER -