An Overview of Results and Conclusions from ITU Segregated Streams/ECOSAN Research Group Experience on Gray Water Management

Baykal A. B.

RECYCLING AND REUSE APPROACHES FOR BETTER SUSTAINABILITY, pp.257-265, 2019 (Peer-Reviewed Journal) identifier


Gray water is a segregated domestic wastewater stream, which may be returned to almost any point in the water cycle after pertinent treatment. It is a reliable and renewable source of water. The experience of ITU's segregated streams and ECOSAN research group has revealed/confirmed some issues/facts about gray water management based on Turkish case studies. Characterization of gray water and/or its sub-streams to be recycled and reused is a key factor in determining final uses as well as selecting the most appropriate treatment schemes and feasible layouts. Pathogens may be as significant a parameter as the predominantly mentioned organic matter. Carefully performed water balances regarding the amount which is to be supplied by reclaimed gray water and the amount of gray water that may possibly be produced within an area are critical in the success and feasibility of the process. Proximity of the gray water source to the location of end use is yet another significant determinant. Economic analysis for reclaimed gray water use for toilet flushing in the Turkish megacity Istanbul has shown that the suggestion is feasible with payback periods of less than 5 years with optimal number of units in developments. Social acceptance surveys indicate that there is a considerable approval for the use of reclaimed gray water. All in all, the idea of recycling and reuse of reclaimed gray water makes a lot of sense, and the conclusions drawn in terms of technical/environmental, economic, and social tiers of sustainability have provided motivating results.