Post-doc Marjolein Vanoppen at the Belgian University of Gent published an idea for an efficient energy neutral process for desalination of sea water.
Desalination of sea water normally is done using a process called reverse osmosis, which uses membranes that allow water to pass through, but keeps the salt behind. This process normally uses a significant amount of energy.
To tackle this problem, Ms Vanoppen had a look at Blue energy, the fancy name for osmotic power. This is a process where almost the reverse takes place: salt from seawater passes through a membrane into sweet water in order to generate electricity.
Now when you generate power using blue energy, you end up with a lot of brackish water. The idea by Ms Vanoppen is to use the brackish water as an input for the production of sweet water. That looks pointless since your input is also sweet water, but the idea is to utilize a sweet wastewater stream like sewage water. This stream cannot easily be converted into drinking water, but is good enough for generating the power needed to desalinate the brackish water.
The final result is an energy neutral process for producing tap water.