This diploma thesis presents the knowledge of wastewater reuse. The theoretical part of the thesis describes types of wastewater (greywater, brownwater, and yellow-water) and their characteristics. Further, the theoretical part describes the possibilities of re-use of wastewater as a source of water in detail, including treatment technology, and the heat recuperation from wastewater. The practical part of the thesis uses gained knowledge for designing a greywater treatment and heat recovery technology of grey water in an apartment complex.