A series of recommendations about the design of desalination intakes and outfalls has been published in a report by the Pacific Institute as part of its series on Key Issues For Seawater Desalination in California.
The report, titled Marine Impacts, examines the affects of desalination intakes on marine life through entraining and impingement, and the introduction of highly concentrated reject brine into seawater.
A review of current understanding of the impacts of intakes is included in the report, with an overview of some of the technological, operational and design measures developed to reduce them, including subsurface intakes. It also includes a review of brine studies that have been conducted at recently completed plants, with a description of observed impacts, and identifies research gaps.
The regulatory system for seawater desalination in California is also examined.
Principle recommendations of the report include:
For intakes:
· Intake pipes should be located outside of areas with high biological productivity and designed to minimize impingement and entrainment.
· Project proponents should thoroughly investigate the feasibility of subsurface intakes, including the evaluation of alternative siting and reduced design capacity of the project.
For outfalls:
· Water managers should avoid disposing of brine in close proximity to sensitive habitats, such as wetlands and some benthic areas.
· Water managers should carefully monitor, report and minimize the impacts of brine disposal on the marine environment.
· More comprehensive studies are needed to determine the impacts of brine on the marine environment and to mitigate these impacts.
The report also calls for more research about the impacts of intakes and brine disposal, and regulators are called on to insist on more monitoring of these impacts.