Desalination can be done through osmosis, which is membrane based. It can also be done through evaporation, which is much less efficient. But if you have a free source of heat, that inefficiency is a non issue.

The waste heat from a steam turbine is higher than boiling. Otherwise the turbine wouldn't work. The boiler turns water into steam, which produces pressure to drive a turbine. The condenser takes the low pressure steam and condenses it back to water.