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Article: Integrated stochastic environmental risk assessment of the Harbour Area Treatment Scheme (HATS) in Hong Kong

TitleIntegrated stochastic environmental risk assessment of the Harbour Area Treatment Scheme (HATS) in Hong Kong
Authors
Issue Date2009
PublisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/est
Citation
Environmental Science And Technology, 2009, v. 43 n. 10, p. 3705-3711 How to Cite?
AbstractSubmarine ocean outfalls are commonly used for the disposal of partially treated effluents in coastal cities. Typically, the greatest environmental risk caused by toxic substances occurs in the near field of the outfall discharge. The ecological impact of the effluent varies greatly under different discharge and environmental conditions that are characterized by both regular and stochastic variations. For a comprehensive environmental risk assessment of a coastal discharge, it is necessary to determine both the likelihood and severity of the adverse effects on the biological community. We present the first integrated stochastic (Monte Carlo) environmental risk assessment of a major coastal sewage outfall discharge - the Stonecutters Island outfall of the Harbour Area Treatment Scheme (HATS) in Hong Kong. Unionized ammonia (NH 3) is used as the target pollutant. To accurately envisage the ambient concentrations of NH3, a Lagrangian jet model (JETLAG/VISJET) is used to analyze pollutant concentrations in the nearfield of the outfall. The environmental conditions are simulated from 3D hydrodynamic model simulations over a 4 month period for typical wet and dry seasons. Statistical characteristics of the effluent discharge and receiving water temperature are derived from field data. The probability distribution of predicted exposure concentrations (EC) is generated from this integrated simulation. A species sensitivity distribution, which represents a statistical distribution of threshold sublethal effects levels or benchmark concentrations (BC) for various marine organisms is constructed using available chronic toxicity data. The environmental risk of NH3 on the marine community is characterized by computing statistical distributions of Hazard Quotient (HQ = EC/BC) using Monte Carlo simulation. It is found that the probability of HQ > 1 for HATS Stage 1 (1.6 million m3/day sewage treated with chemically enhanced primary treatment) is around 0.11 for wet season but just about 0.06 for the dry season. The risk increases by about 10% to 0.08-0.13 with additional sewage loads of 0.8 million m3/day at the same level of treatment (HATS Stage 2A). With an upgrade to secondary treatment (HATS Stage 2B), the probability will be reduced to 0.03-0.05. Compared to the use of "worst case" scenarios or point pollution threshold estimates, the present method offers a more holistic ecological assessment, and is much less sensitive to arbitrary choice of model parameters. The present risk assessment approach can be readily extended to the accurate determination of mixing zones based on statistical evaluation of ecological risks. © 2009 American Chemical Society.
Persistent Identifierhttp://hdl.handle.net/10722/58485
ISSN
2015 Impact Factor: 5.393
2015 SCImago Journal Rankings: 2.664
ISI Accession Number ID
Funding AgencyGrant Number
University Grants Committee of the Hong Kong Special Administrative Region (HKSAR), ChinaAoE/P-04/04
Funding Information:

The work reported herein is supported by a grant from the University Grants Committee of the Hong Kong Special Administrative Region (HKSAR), China (Project No. AoE/P-04/04) to the Area of Excellence in Marine Environment Research and Innovative Technology (MERIT). The assistance of the Environmental Protection Department, HKSAR Government in providing the current velocity field data is gratefully acknowledged. We also thank Dr. Gilbert Lui for his assistance in the statistical analysis for constructing the SSDs.

References

 

DC FieldValueLanguage
dc.contributor.authorChoi, KWen_HK
dc.contributor.authorLee, JHWen_HK
dc.contributor.authorKwok, KWHen_HK
dc.contributor.authorLeung, KMYen_HK
dc.date.accessioned2010-05-31T03:31:16Z-
dc.date.available2010-05-31T03:31:16Z-
dc.date.issued2009en_HK
dc.identifier.citationEnvironmental Science And Technology, 2009, v. 43 n. 10, p. 3705-3711en_HK
dc.identifier.issn0013-936Xen_HK
dc.identifier.urihttp://hdl.handle.net/10722/58485-
dc.description.abstractSubmarine ocean outfalls are commonly used for the disposal of partially treated effluents in coastal cities. Typically, the greatest environmental risk caused by toxic substances occurs in the near field of the outfall discharge. The ecological impact of the effluent varies greatly under different discharge and environmental conditions that are characterized by both regular and stochastic variations. For a comprehensive environmental risk assessment of a coastal discharge, it is necessary to determine both the likelihood and severity of the adverse effects on the biological community. We present the first integrated stochastic (Monte Carlo) environmental risk assessment of a major coastal sewage outfall discharge - the Stonecutters Island outfall of the Harbour Area Treatment Scheme (HATS) in Hong Kong. Unionized ammonia (NH 3) is used as the target pollutant. To accurately envisage the ambient concentrations of NH3, a Lagrangian jet model (JETLAG/VISJET) is used to analyze pollutant concentrations in the nearfield of the outfall. The environmental conditions are simulated from 3D hydrodynamic model simulations over a 4 month period for typical wet and dry seasons. Statistical characteristics of the effluent discharge and receiving water temperature are derived from field data. The probability distribution of predicted exposure concentrations (EC) is generated from this integrated simulation. A species sensitivity distribution, which represents a statistical distribution of threshold sublethal effects levels or benchmark concentrations (BC) for various marine organisms is constructed using available chronic toxicity data. The environmental risk of NH3 on the marine community is characterized by computing statistical distributions of Hazard Quotient (HQ = EC/BC) using Monte Carlo simulation. It is found that the probability of HQ > 1 for HATS Stage 1 (1.6 million m3/day sewage treated with chemically enhanced primary treatment) is around 0.11 for wet season but just about 0.06 for the dry season. The risk increases by about 10% to 0.08-0.13 with additional sewage loads of 0.8 million m3/day at the same level of treatment (HATS Stage 2A). With an upgrade to secondary treatment (HATS Stage 2B), the probability will be reduced to 0.03-0.05. Compared to the use of "worst case" scenarios or point pollution threshold estimates, the present method offers a more holistic ecological assessment, and is much less sensitive to arbitrary choice of model parameters. The present risk assessment approach can be readily extended to the accurate determination of mixing zones based on statistical evaluation of ecological risks. © 2009 American Chemical Society.en_HK
dc.languageengen_HK
dc.publisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/esten_HK
dc.relation.ispartofEnvironmental Science and Technologyen_HK
dc.subject.meshAmmoniaen_HK
dc.subject.meshEnvironmenten_HK
dc.subject.meshGeographyen_HK
dc.subject.meshHong Kongen_HK
dc.subject.meshRisk Assessmenten_HK
dc.subject.meshSewageen_HK
dc.subject.meshSpecies Specificityen_HK
dc.subject.meshStochastic Processesen_HK
dc.subject.meshTropical Climateen_HK
dc.subject.meshWater Pollutionen_HK
dc.titleIntegrated stochastic environmental risk assessment of the Harbour Area Treatment Scheme (HATS) in Hong Kongen_HK
dc.typeArticleen_HK
dc.identifier.emailChoi, KW: choidkw@hkucc.hku.hken_HK
dc.identifier.emailLee, JHW: hreclhw@hku.hken_HK
dc.identifier.emailLeung, KMY: kmyleung@hku.hken_HK
dc.identifier.authorityChoi, KW=rp00107en_HK
dc.identifier.authorityLee, JHW=rp00061en_HK
dc.identifier.authorityLeung, KMY=rp00733en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1021/es803244sen_HK
dc.identifier.pmid19544877-
dc.identifier.scopuseid_2-s2.0-66249147226en_HK
dc.identifier.hkuros155925en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-66249147226&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume43en_HK
dc.identifier.issue10en_HK
dc.identifier.spage3705en_HK
dc.identifier.epage3711en_HK
dc.identifier.isiWOS:000266046700050-
dc.publisher.placeUnited Statesen_HK
dc.identifier.scopusauthoridChoi, KW=25627214800en_HK
dc.identifier.scopusauthoridLee, JHW=36078318900en_HK
dc.identifier.scopusauthoridKwok, KWH=19337480200en_HK
dc.identifier.scopusauthoridLeung, KMY=7401860738en_HK

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