Recent Papers on Marine Outfalls

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Underwater and underused: The case for marine outfalls in wastewater disposal

Water21 October 2010 (Issue 12.5) pp22-26 © IWA Publishing

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Philip Roberts

The idea of using marine outfalls for the disposal of wastewater can be poorly received, despite evidence of their effectiveness and low impact. Philip Roberts outlines the advantages of using marine outfalls, and recent advances in technology and research of the impacts of marine wastewater disposal.

Carbon and nitrogen stable isotopes in coastal benthic populations under multiple organic enrichment sources

Marine Pollution Bulletin Vol60 Issue 10 pp 1790-1802 © Elsevier 2010

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Leandro Sampaioa, Ana Maria Rodriguesa and Victor Quintinoa
aCESAM, Department of Biology, University of Aveiro, 3810-193 Aveiro, Portugal


In a dispersive coastal area under multiple organic enrichment sources, stable isotopes were used to trace organic sources of carbon and nitrogen in sediments and benthic macrofauna. The Bivalve Abra alba and the Polychaetes Nephtys sp. and Pectinaria (Lagis) koreni were reliable indicators of the input of terrestrial-derived organic matter into this coastal area, either originated in outfall sewage discharges or estuarine outflow. An isotopic depletion was observed up to 250 m from the outfall branches, much stronger in the biota than in the sediments. An enrichment of 2‰ in the sediments, and 2–6‰ in the species was noticed in sites located farther than 1500 m from the outfall. Depositivores and carnivores/omnivores gave the best picture of the extension of the sewage dispersion and incorporation into the food web.

Simulation of Jeddah multi-port sea outfall

Journal of Coastal Conservation Vol 14 No 1 pp 63-69 © Springer 2010

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Abdullah S. Al-Ghamdi
Civil Engineering Department, King Abdulaziz University,
P.O. Box 80204, Jeddah 21589, Saudi Arabi, e-mail:


Jeddah wastewater multi-port outfall was analyzed using CORMIX2 for average ambient conditions. The numerical analysis of the outfall shows that the near-field mixing extends 187.5 m downstream of the diffuser and the dilution at the end of near-field reaches 1,047.8. The concentration of the plume drops sharply from 100 at the exit point to 0.0954 at the end of near-field zone. In the far-field zone the reduction in concentration is gradual and will reach 0.0061 at a distance of 20,000 m downstream of the diffuser, while dilution exceeds 16,440 at this point. The plume rises rapidly due to the buoyancy and touches the water surface at a distance of 187.5 m downstream. The thickness of the plume reaches a maximum value of 37.5 m at the interface of near-field and far-Field zones, and then it starts spreading horizontally maintaining a thickness of about 13 m over a distance of about 4 km. As the plume mixes with ambient sea water, it starts spreading again in vertical direction and fills the entire water depth at a distance of 18,927 m down stream. The plume maintains nearly a constant width in the near-field zone but spreads progressively horizontally in the far-field zone till the plume touches the left bank at a distance of 18,482.52 m downstream. The plume spreads at a distance of 2,069 m from the coastline at the end of simulation zone. It can be concluded from numerical results that if the discharged water meets local and international standards for treated wastewater, the plume will not pose any threats to the local venerable environment as the dilution is considerably high due to high exit momentum and favorable cross current.

Membrane bioreactor application in wastewater re-use from the effluent of Bali primary WWTP, northern Taiwan

Water Science & Technology Vol 53 No 9 pp 131–140 © IWA Publishing 2006

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H.H. Chen*, S. Shiau** and Y.C. Lin***

*Center for Environmental, Safety and Health Technology Development, Industrial Technology Research Institute, Taiwan; Associate Professor, National United University, Taiwan, (E-mail:
**Center for Environmental, Safety and Health Technology Development, Industrial Technology Research Institute, Taiwan, (E-mail:
***Engineer, Green Environmental Technology Co. Ltd., Taiwan, (E-mail:


Two MBR pilot systems were constructed and tested in the Bali Primary WWTP. The pilot study shows that two MBR systems, i.e. the Green-MenBio system (MBR-1) and the Bio-MF system (MBR-2), can both fulfill the requirement of wastewater reclamation standard. The MBR-2 system is more economical compared with MBR-1 system. The cost of US$ 0.10-0.16/m3 is estimated to reclaim the effluent of primary WWTP in Taiwan. The Bali Primary WWTP has the capacity of 1,320,000 cmd which is the biggest in Taiwan. The domestic wastewater of partial Taipei City and Taipei County are collected and transported to the Bali Primary WWTP. The effluent of the Bali Primary WWTP is then discharged into the ocean through two 3.8 m marine outfalls. The AO processes are installed in both MBR systems. More than 90% of the NH3-N can be removed through the AO and membrane processes. The outflow of the MBR systems (without RO) can reach the quality of COD <30 mg/l, BOD <10 mg/l, SS <5 mg/l, NH3-N <3 mg/L. The outflow of the MBR system is proposed to transport 40 km south to the Taoyuan County where four new industrial parks are to be constructed. Part of the reclaimed water is to be used on irrigation and another portion is to be sent to the industries after RO treatment.

Planning of wastewater treatment and disposal systems of Istanbul metropolitan area

Water Science & Technology Vol 44 No 2-3 pp 31–38 © IWA Publishing 2001

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V. Eroglu*, H.Z. Sarikaya** and A.F. Aydin***

*Istanbul Water and Sewerage Administration (ISKI), Inkilap Cd. No: 34 Aksaray, Istanbul, Turkey
**Istanbul Water and Sewerage Administration (ISKI), Inkilap Cd. No: 34 Aksaray, Istanbul, Turkey
***Istanbul Technical University, Department of Environmental Engineering, 80626, Maslak, Istanbul, Turkey


Current and future wastewater treatment and disposal strategies of Istanbul city are presented. Istanbul is the largest city of Turkey and has a population of 10 million that may reach about 20 million in 2032. The city is divided into Asian and European sides by the Bosphorus Strait. The Sea of Marmara is an enclosed sea, connected to the Black Sea and Aegean Sea by the straits of Bosphorus and Dardanelles. Therefore, there is very strong and permanent stratification in the Sea of Marmara throughout the year, lower layers carrying Mediterranean and the upper layers carrying Black Sea water. This unique coastal structure of Istanbul necessitated a detailed study to determine the level of wastewater treatment and the location and depth of marine outfalls. A comprehensive three-dimensional water quality modelling study concluded that tertiary treatment including nitrogen and phosphorus removal is required for the effluent discharges into the Marmara Sea. However, enhanced primary or even primary treatment has been found satisfactory for discharges into the lower layers of the Bosphorus and into the Black Sea. Provisions for upgrading to secondary treatment were recommended. The status of existing and planned wastewater treatment plants and sea outfalls of Istanbul city are also presented. Although the amount of treated wastewater was only 63 percent in 1998, a target of 95 percent treatment level by the end of 2000 has been adopted in implementation plans. All treatment plants are located at or close to the coast except Pasakoy WWTP which is in the catchment area of Omerli Reservoir, the major source of drinking water for Istanbul city. The Pasakoy WWTP has been designed to treat wastewaters collected from the catchment area of Omerli Reservoir to tertiary level before ultimate disposal. The implementation programme together with the cost estimates are given. Total investment on water, wastewater and stormwater projects up to year 2032 is estimated at about 10 billion US Dollars. The share of the wastewater projects in this total is increasing with time. The financial analysis concluded that investments for a Higher Demand Scenario can be realised by raising the water tariffs to 1.0 $/m3 for Phase 1 and 0.9 $/m3 for Phase 2.

Marine sewage outfall assessment for the capital regional district, British Columbia, using nested three-dimensional models

Water Science and Technology Vol 38 No 10 pp 301–308 © IWA Publishing 1998

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D. O. Hodgins*, S. W. Tinis* and L. A. Taylor**

*Seaconsult Marine Research Ltd, 8805 Osler Street Vancouver V6P 4G1 Canada
**Capital Regional District, P.O. Box 1000 Victoria V8W 2S6 Canada


Nested three-dimensional, prognostic hydrodynamic and coupled transport-diffusion models were developed to simulate the dispersion of contaminants from two large marine outfalls discharging untreated sewage effluent into the estuarine waters of Juan de Fuca Strait. The modelling system is comprised of a 200-m fine grid model nested inside a 1-km large area model incorporating all estuarine circulation processes, and an embedded version of the UM buoyant diffuser plume model. Predictions for fecal coliform distributions were successfully verified using observations obtained during a monitoring program in December 1996.

Experimental observations of salt purging in a model sea outfall diffuser with eight soffit connected risers

Water Science and Technology Vol 38 No 10 pp 269–275 © IWA Publishing 1998

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R. Burrows*, K. H. M. Ali*, K. Spence** and T. T. Chiang***

*Department of Civil Engineering, University of Liverpool L69 3BX UK
**Department of Civil & Structural Engineering, University of Sheffield UK
***Ministry of Agriculture Malaysia, Ampang Jajar, 05990 Alor Setar Kedah Darul Aman Malaysia


Improved rehabilitation design for the long-term hydraulic function of marine outfalls with soffit connected risers is the main aim of the research programme reported here. As a step towards this goal a better understanding of the processes of saline intrusion and saltwater purging has been developed from detailed laboratory studies. Unsteady flow cycles have been investigated and observed riser purging sequences have been compared against theoretical criteria. From the monitoring of riser flow salinity, quantitative measures of the salt wedge front entrainment process have been obtained together with indicative figures for salt wedge expulsion rate. This interim outcome is intended to alert the designer and operator of outfalls of the potential problems with soffit connected riser systems.

Wastewater treatment utilizing submarine outfalls: the role of science, communications and public involvement in the decision-making process

Water Science and Technology Vol 32 No 2 pp 1–8 © IWA Publishing 1995

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Vernon J. Rogers

Capital Regional District, Head, Environmental Services Group, 524 Yates Street, P.O. Box 1000 Victoria, B.C., V8W 2S6 Canada


In Victoria, British Columbia, Canada, sewage is discharged to the marine environment after preliminary treatment by screening. In 1992, the CRD undertook related technical investigations including studies of the ocean sediments in the area of the two main outfalls. The results of these investigations, together with information concerning other aspects of liquid waste management, were then described as part of a public involvement program which culminated in a referendum held in November 1992. The referendum invited the public to choose from three options for land-based sewage treatment. All three options included programs such as source control, that offered clear environmental benefits. The majority of voters (56%) decided in favour of the option which includes continuation of the existing level of sewage treatment. This paper describes the process followed, and shows how good science, effective communication, and public involvement can aid a rational approach to decision-making about marine environmental management and wastewater treatment utilizing submarine outfalls. It also highlights some important points concerning development of community and environmental priorities, identification of stakeholders, public involvement, and the role of independent scientific assessment.

Evaluation of hydrodynamic characteristics of the Bosphorus regarding the performance of the marine outfall systems

Water Science and Technology Vol 32 No 2 pp 85–93 © IWA Publishing 1995

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Adnan Akyarli and Yalçin Arisoy

Dokuz Eylul University, Institute of Marine Science and Technology (IMST), P.O.B. 478 35211 Izmir Turkey


Considering strong interrelations between hydrodynamic features of the Bosphorus and the tube-tunnel crossing which may affect the performance of marine outfall systems, the Institute of Marine Science and Technology (IMST) conducted a comprehensive meteo-oceanographic data acquisition campaign to collect information both for the reliable design of marine outfall systems and for the environmental impact assessment (EIA) of the railroad tunnel, on the joint request of the owners of the projects.

The main objectives of this paper are to outline the results of the EIA, and also to discuss the newly adopted plan which proposes to divert the sewage collected in the Kadìköy drainage area to Riva, located along the Black Sea. Recent evaluations by the authors on the blocking of lower layer flow, and findings presented on the mixing along the Bosphorus, have been included as scientific evidences in this discussion.

Diffuser design for marine outfalls in areas with strong currents, high waves and sediment transport

Water Science and Technology Vol 32 No 2 pp 249–255 © IWA Publishing 1995

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Torben Larsen

Aalborg University, Department of Civil Engineering, Environmental Hydraulics Group, Sohngaardsholmsvej 57 DK-9000 Aalborg Denmark


The design of marine outfalls is often based on environmental criteria for a minimum initial dilution. Accordingly advanced diffuser arrangement are designed to fulfil these requirements. A large number of examples of malfunction and blocking in sea outfalls have occurred around the world as a result of this uncompromising consent to environmental demands. Two examples of unconventional design are given in this paper. Both cases involved risk of blockage of the diffuser section because of wave and current induced sediment transport. The paper also discusses how acceptable far field dilution conditions can be achieved even if normally accepted initial criteria are not fulfilled.

Case studies on preliminary treatment facilities at marine outfalls

Water Science and Technology Vol 32 No 2 pp 265–271 © IWA Publishing 1995

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H. Huber*, A. B. Tanik** and M. Gerçek*

*Hans Huber GmbH, Maschinen und Anlagenbau, Maria-Hilf Strasse 3-5 92334 Berching Germany
**I.T.Ü. Civil Engineering Faculty, Environmental Sciences Division 80626 Maslak, Istanbul Turkey


As with many coastal discharges, the search for a suitable primary treatment system has long been accepted as a first stage treatment of both municipal and industrial wastewater. Over the last decade, milliscreening has almost become the best alternative method among the conventional systems applicable to marine outfall treatment. This paper, summarizes three case studies using milliscreening equipment with variable bar spacings on treatment facilities at marine outfalls. The best solution was achieved at Poverty Bay in New Zealand where the bar spacing was 1 mm. The other two applications were attempted in United Kingdom. The milliscreens of 10 mm at Tonyrefail and 5 mm at Wooler were not able to meet the required performance. In regard of these studies, it is recommended that finer screens with bar spacing of less than 5 mm are likely to provide adequate performance when used to screen marine outfalls.

Dilution studies on three marine outfalls in South Africa

Water Science and Technology Vol 32 No 2 pp 297–304 © IWA Publishing 1995

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Willem A. M. Botes* and J. F. Kapp**

*CSIR, Ematek, P. O. Box 320 Stellenbosch South Africa
**GFJ Inc. Consulting Engineers, De Waterkant, 10 Helderberg St Stellenbosch South Africa


Field dilution studies were conducted on three "deep" water marine outfalls located along the South African coast to establish the comparibility of actual achievable initial dilutions against the theoretical predicted values and, where appropriate, to make recommendations regarding the applicability of the different prediction techniques in the design of future outfalls.

The physical processes along the 3000 km long coastline of South Africa are diverse, ranging from dynamic sub-tropical waters on the east coast to cold, stratified stagnant conditions on the west coast. Fourteen existing offshore marine outfalls serve medium to large industries and various local authorities (domestic effluent). For this investigation three outfalls were selected to represent the range of outfall types as well as the diversity of the physical conditions of the South African coastline.

The predicted dilutions, using various approaches, compared well with the measured dilutions. It was found that the application of more "simple" prediction techniques (using average current velocities and ambient densities) may be more practical, ensuring a conservative approach, in pre-feasibility studies, compared to the more detailed prediction models, which uses accurate field data (stratification and current profiles), when extensive field data is not readily available.

Bacterial die-away rates in red sea waters

Water Science and Technology Vol 32 No 2 pp 45–52 © IWA Publishing 1995

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H. Z. Sarikaya


Total coliform bacteria have been chosen as the indicator organism. Coliform die-away experiments have been carried out in unpolluted sea water samples collected at about 100 m off the coastline and under controlled environmental conditions. The samples were transformed into one litre clean glass beakers which were kept at constant temperature and were exposed to the solar radiation. The membrane filter technique was used for the coliform analysis. The temperature ranged from 20 to 40o C and the dilution ratios ranged from 1/50 to 1/200.

Coliform decay rate in the light has been expressed as the summation of the coliform decay rate in the dark and the decay rate due to solar radiation. The solar radiation required for 90 percent coliform removal has been found to range from 17 cal/cm2 to 40 cal/cm2 within the temperature range of 25 to 30o C. Applying the linear regression analysis two different equations have been given for the high (I>10 cal/cm2.hour) and low solar intensity ranges in order to determine the coliform decay rate constant as a function of the solar intensity.

T-90 values in the light have been found to follow log-normal distribution with a median T-90 value of 32 minutes. The corresponding T-90 values in the dark were found to be 70-80 times longer. Coliform decay rate in the dark has been correlated with the temperature.

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