In the area around Sydney, Australia, several private organizations have found a new dependable source of water for irrigation and other non-potable uses - the sewer. The idea is to tap into sewer lines, treat the water to make it suitable for irrigation, and thereby save drinking water for - drinking. Four such projects have already been completed and eight more are planned.
As explained in a National Geographic article:
"When well planned and designed, sewer mining can yield a variety of benefits. It can relieve overtaxed wastewater systems, trim water and wastewater infrastructure costs, reduce energy and chemical use, and save drinking water for activities that really need drinking-quality water. These water-savings, in turn, can help keep more water in rivers, lakes and streams – which is especially crucial during droughts and summer months, when river flows are low and water demands are high."