Table 1.

Definitions of planned and unplanned forms of wastewater reuse.

Wastewater reuse type	Planned/unplanned	Mechanism
De facto reuse	Unplanned	Wastewater treatment plant effluent is discharged to surface water and later drawn into a downstream city’s water treatment facility.
Indirect potable reuse (IPR)	Planned	Wastewater treatment plant effluent is purified using advanced water treatment technology and then pumped back into the existing water supply source (same city), where it mixes with in-situ water before being drawn back into supply via existing infrastructure.
Direct potable reuse (DPR)	Planned	Wastewater treatment plant effluent is purified using advanced water treatment technology then supplied directly back into the distribution system serving the same city.