According to the article, because of the method of desalination, and likely because of the fairly small amount of water that each bouy can process and harvest, they say that the brine that’s separated from the freshwater is of low enough salt concentration that it should not damage the ecosystem, so they just dump the brine back in the ocean, presumably below the bouy itself.

They also mentioned that one of these buoys as currently designed can provide water for about 43 houses, and that their plan to scale up is to just add more buoys. If they add enough of these buoys in a given area to make a meaningful contribution to a community’s freshwater requirements, with each of them individually contributing in a relatively small way to a higher concentration of salt in the local seawater, what does that add up to? How many of these can you put in an area before you are raising the salinity in a given area to a level that’s harmful to the ecosystem?