Grey water treatment and circular economy

Owing to the continuous decline in freshwater availability in many parts of the world, emphasis has been placed on sustainable utilization of available water. The reuse of treated wastewater generated from household activities, especially greywater, for non-potable purposes, could be a solution to the current situation. Several technologies have been developed for greywater treatment. The quality of greywater varies depending on the products being used for household activities; therefore, no single process can treat greywater up to the required quality standard for a long duration. Various combinations of treatment processes have been tested worldwide. The residue produced during the treatment process was promoted for use as a resource. This review focuses on the reported greywater characteristics, treatment technologies available for greywater, and technologies reported for the reuse of residues produced after greywater treatment.