Screening the hurdles to sea disposal of desalination brine around the Mediterranean

As desalination develops, the impacts of brine ocean disposal rise increasing concerns. Here we present a screening of the hurdles to brine disposal through pressurized submerged outfalls in the broader Mediterranean region. Using first-tier dilution models, we analyze how different environmental quality standards reflect in terms of initial outfall velocity. We show that achieving moderate dilution is usually not problematic, while higher environmental quality standards would often require excessively high initial velocities. Although this may not be so overwhelming a problem as to undermine the feasibility of brine discharge, it indicates possible hurdles to arise in the permitting of a project. We also show that increasing water recovery (i.e. having more concentrated brine) reduces jet extents, hence allows disposal in shallower waters, with smaller pipelines, causing an appreciable reduction of costs, while also slightly reducing pumping energy demand (which is rather small anyway in comparison with the overall energy demand of the desalination process). This makes recovery of water from the brine a potentially interesting management option, to be appraised against the costs of increasing recovery, and the difficulties arising from the higher dilution required at the outfall. •Brine disposal may be a significant hurdle for the permitting of desalination plants in the Mediterranean.•A large percentage of the potentially served population may require complex outfall design.•When dilution requirements are met , concentrating the brine beyond typical recovery would reduce the distance of disposal from the coast, and cut on disposal costs.•Further brine concentration should be appraised in relationship with the costs of increasing recovery.