Due to the difference in density between the discharge effluent and coastal water,partially treated wastewater is often discharged into the marine environment as a buoyant jet via submarine outfalls with multiport dif...Due to the difference in density between the discharge effluent and coastal water,partially treated wastewater is often discharged into the marine environment as a buoyant jet via submarine outfalls with multiport diffusers.The dilution characteristics of effluent discharge(dual buoyant jets)in a wavy cross-flow environment were studied in a laboratory.The planar laser-induced fluorescence technique was used to obtain the concentration data of the jets.The effects of different environmental variables on the diffusion and dilution characteristics of the jets were examined through physical experiments,dimensional analysis,and empirical formulations.It was found that the dilution process of the dual jets could be divided into two components:the original jet component and the effluent cloud component.The jet-to-current velocity ratio was the main parameter affecting the concentration levels of the effluent cloud.The merging of the two jets increased the jet concentration in the flow field.When the jets traveled further downstream,the axial dilution increased gradually and then increased significantly along the axis.Under the effects of strong waves,the concentration contours branched into two peaks,and the mean dilution became more significant than under the effects of weak waves.Therefore,the dilution of the effluent discharge was expected to be significant under strong wave effects because the hydrodynamic force increased.A dilution equation was derived to improve our understanding of the dilution process of buoyant jets in a wavy cross-flow environment.This equation was used to determine the influences of the jet-to-current velocity ratio,wave-to-current velocity ratio,and Strouhal number on the minimum jet dilution.It revealed that the wave and buoyancy effects in effluent discharges were significant.展开更多
Global ocean acidification driven by atmospheric CO 2 uptake is well recognized;however,coastal zones are subject to additional,localized acidification pressures.Among these,the chronic discharge of low-pH-treated was...Global ocean acidification driven by atmospheric CO 2 uptake is well recognized;however,coastal zones are subject to additional,localized acidification pressures.Among these,the chronic discharge of low-pH-treated wastewater(often pH 6.0),permitted under many current regulations,represents a significant but often overlooked stressor.This practice introduces highly acidic loads into sensitive nearshore ecosystems that are chemically incompatible with ambient seawater(pH~8.1).This perspective argues for reframing effluent pH not only as a pollutant parameter to be bounded but also as a modifiable policy lever.Revising discharge standards to require a minimum effluent pH>8.0 for marine outfalls offers a novel pathway to mitigate localized coastal acidification.Furthermore,this approach aligns with emerging ocean alkalinity enhancement strategies,potentially enhancing coastal carbon sequestration and offering cobenefits such as reduced metal toxicity.Such a policy shift necessitates technological adaptation but promises significant benefits for coastal resilience and broader ocean sustainability goals.展开更多
基金supported by the Fundamental Research Funds for the Central Universities of China(Grant No.B200202057)and the National Natural Science Foundation of China(Grant No.51979076)。
文摘Due to the difference in density between the discharge effluent and coastal water,partially treated wastewater is often discharged into the marine environment as a buoyant jet via submarine outfalls with multiport diffusers.The dilution characteristics of effluent discharge(dual buoyant jets)in a wavy cross-flow environment were studied in a laboratory.The planar laser-induced fluorescence technique was used to obtain the concentration data of the jets.The effects of different environmental variables on the diffusion and dilution characteristics of the jets were examined through physical experiments,dimensional analysis,and empirical formulations.It was found that the dilution process of the dual jets could be divided into two components:the original jet component and the effluent cloud component.The jet-to-current velocity ratio was the main parameter affecting the concentration levels of the effluent cloud.The merging of the two jets increased the jet concentration in the flow field.When the jets traveled further downstream,the axial dilution increased gradually and then increased significantly along the axis.Under the effects of strong waves,the concentration contours branched into two peaks,and the mean dilution became more significant than under the effects of weak waves.Therefore,the dilution of the effluent discharge was expected to be significant under strong wave effects because the hydrodynamic force increased.A dilution equation was derived to improve our understanding of the dilution process of buoyant jets in a wavy cross-flow environment.This equation was used to determine the influences of the jet-to-current velocity ratio,wave-to-current velocity ratio,and Strouhal number on the minimum jet dilution.It revealed that the wave and buoyancy effects in effluent discharges were significant.
基金supported by the Ocean Negative Carbon Emissions(ONCE)Program and the National Natural Science Foundation of China(42188102,42376148).
文摘Global ocean acidification driven by atmospheric CO 2 uptake is well recognized;however,coastal zones are subject to additional,localized acidification pressures.Among these,the chronic discharge of low-pH-treated wastewater(often pH 6.0),permitted under many current regulations,represents a significant but often overlooked stressor.This practice introduces highly acidic loads into sensitive nearshore ecosystems that are chemically incompatible with ambient seawater(pH~8.1).This perspective argues for reframing effluent pH not only as a pollutant parameter to be bounded but also as a modifiable policy lever.Revising discharge standards to require a minimum effluent pH>8.0 for marine outfalls offers a novel pathway to mitigate localized coastal acidification.Furthermore,this approach aligns with emerging ocean alkalinity enhancement strategies,potentially enhancing coastal carbon sequestration and offering cobenefits such as reduced metal toxicity.Such a policy shift necessitates technological adaptation but promises significant benefits for coastal resilience and broader ocean sustainability goals.
