Methods, systems, and/or apparatuses for treating wastewater produced at a thermoelectric power plant, other industrial plants, and/or other industrial sources are disclosed. The wastewater is directed through a wastewater concentrator including a direct contact adiabatic concentration system. A stream of hot feed gases is directed through the wastewater concentrator. The wastewater concentrator mixes the hot feed gases directly with the wastewater and evaporates water vapor from the wastewater. The wastewater concentrator separates the water vapor from remaining concentrated wastewater. A contained air-water interface liquid evaporator may be arranged to pre-process the wastewater before being treated by the wastewater concentrator.