Energy-efficient gasification-based multi-generation apparatus, facilities, or systems, and methods of modifying existing gasification-based multi-generation apparatus and the various conventional thermal coupling arrangements, are provided. An exemplary gasification-based multi-generation apparatus includes a gasification system configured to generate the raw syngas feed from a carbon-based feedstock. The gasification system includes a gasification plant or facility, a sour water stripping plant or facility comprising a sour water stripper, a gasification reactor, and a gasification system energy management system. The gasification system energy management system comprises a third gasification system process-to-process heat exchanger unit positioned to receive a wastewater bottom stream from the sour water stripper and to receive at least a portion of an oxygen feed to the gasification reactor to provide heat energy to the at least a second portion of the oxygen feed to the gasification reactor and to cool the wastewater bottom stream from the sour water stripper. The sour water stripping plant or facility is integrated into the gasification plant or facility through at least the wastewater bottom stream from the sour water stripper.