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Shifting the Discharge Mind-Set from Harmful to Habitat: Exploring Inventive Designs and Benefits of Underwater Discharge Structures

Author(s): Riaan Van der Merwe

Linked Author(s): Riaan Van der Merwe

Keywords: Desalination; Concentrate discharge; Underwater discharge structures; Habitat; Environmental impact assessment; Building with nature;

Abstract: Most countries in the Middle East and other parts of the world depend on seawater desalination to provide in their fresh water needs. The demand for desalinated water is also expected to continue growing for the foreseeable future. As part of the desalination process, fresh water is extracted from seawater leaving a brine effluent that is typically discharged back into the marine environment.
With the aim to protect the marine environment, regulations have been set to regulate the brine discharges, and defining environmental criteria in the area close to the outfall. It was however noted, that such criteria are often adopted from generic benchmarks and sometimes from unadoptable locations. Robust and in situ research on the effects of the brine effluent on the marine environment is also lacking. Recent surveys however suggest that the ecological impact of brine outfalls can be very limited or even result in an improvement of biodiversity and marine abundance on the outfall structure. Such observations suggest that some environmental criteria may be archaic, which may result in needlessly expensive outfall designs.
Additionally, the hard substrate that the outfall structure provides appears to be a good habitat for the enhancement of marine growth. This was already observed in other cases, such as wind farms in the North Sea and several existing outfalls. We therefore propose, instead of only aiming to minimise impact, also to promote the ecological habitat function by optimising design criteria of underwater discharge structures. Our paper presents first guidelines/examples (of shapes and material use (e.g. coating with eco concrete)) to promote coral growth, nursery ground for fish etc. Furthermore, we provide initial ideas for the treatment of the desalination effluent to help the advancement of such marine habitats.

DOI: https://doi.org/10.3850/38WC092019-5552

Year: 2019

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