Energy is an expensive production resource. To save energy we`ve relied since 1986 on the energy efficient process of direct vapor recompression. The industrial wastewater is evaporated under a slight vacuum. This reduces the boiling temperature of the water. The emerging steam is compressed to ambient, normal pressure and heated up by means of a vapor compressor. The energy of the hot steam is recycled to evaporate the wastewater. Due to the energy recycling in the waste water evaporator no additional evaporation energy is required. The electrical motor of the vapor compressor is the sole energy consumer in the wastewater evaporator system.