Venturi diffusers as enhancing devices for the dilution process in desalination plant brine discharges

Abstract

Brine discharges from desalination plants spread out over broad spatial scales, affecting the benthic communities encountered along the way. Because of this, it is essential to develop technology enhancement initiatives for brine discharge processes that are economically feasible and effective for both planned and existing desalination plants. The technical feasibility of using venturi diffusers rather than conventional devices to enhance dilution processes was studied at the Maspalomas II desalination plant, in the south of the island of Gran Canaria (Canary Islands-Spain). The venturi eductors needed very high exit velocities (⩾11 m/s) to reach the pressure difference required to produce the suction effect of these devices. At these velocities, the venturi eductors were more efficient than conventional diffusers, as they achieved much higher dilutions of around 39 as opposed to 27. Dilutions as high as these are not only very useful, but also necessary, as part of the island’s largest and most ecologically important seagrass meadow of Cymodocea nodosa is found nearby.

Keywords:

• Brine discharges
• Desalination
• Diffusers
• Eductor
• Venturi
• Dilution
• Seagrasses
• Cymodocea nodosa

Acknowledgments

This study was conducted as part of the project “Technical feasibility study of venturi diffusers in desalination plant brine discharges to enhance the dilution process and reduce the environmental impact on marine ecosystems”, under the Spanish National Programme for Experimental Development Projects, within the Ministry of the Environment and Rural and Marine Affairs, Environment and Eco-Innovation Sector, Management and Sustainable Uses of Natural Resources Subsection. The authors are grateful to A. Arencibia, F. Roch, from General Electrics, and to A. Ruiz, from CEDEX, for their support, and J. McGrath, for translation of the manuscript from Spanish.

Notes

Presented at the International Conference on Desalination for the Environment, Clean Water and Energy, European Desalination Society, 23–26 April 2012, Barcelona, Spain