https://phys.org/news/2019-01-environment-solutions-problems.html

A study released Monday shows for the first time that more than 16,000 desalination plants scattered across the globe produce more briny toxic sludge than fresh water.

For every litre of fresh water extracted, a litre-and-a-half of salty, chemical-laden sludge called brine is dumped—in most cases—into the ocean.