An apparatus for evaporating waste water and reducing gas emissions includes an evaporator device (7, 31) configured to receiving a portion of flue gas emitted from a boiler unit (1) and waste water to directly contact the flue gas with the waste water to cool and humidify the flue gas and to dry solid particulates within the waste water. In some embodiments, the waste water may be a component of a mixture formed by a mixer device (25) prior to being contacted with the flue gas to humidify and cool the flue gas and dry solids within the waste water. An alkaline reagent as well as activated carbon can be mixed with the waste water prior to the waste water contacting the flue gas. Solid particulates that are dried within the cooled and humidified flue gas can be separated from the flue gas via a particulate collector (9).