For the last six years, a power plant in San Luis Potosi, Mexico has bought water from a nearby wastewater treatment plant to use in its cooling towers (instead of using freshwater). This operation, Project Tenorio, a public-private partnership, continues today and has already resulted in the reduction of groundwater extraction of at least 48 million cubic meters (equivalent to 19,000 Olympic size pools) and increased aquifer sustainability.
This is a good example of the water and energy nexus in practice: the wastewater treatment plant covers almost all of its operating costs from this additional revenue stream and the power plant gets a more reliable water source that is also 33% cheaper than groundwater in that area.
Treated wastewater has been used to reduce the water requirements of power plants in several other countries as well, as water supply becomes more variable or disappears. In the US, for example, around 50 power plants are using treated wastewater for cooling in order to adapt to water shortages. However, innovative integrated approaches like these are still more of an exception than the norm.