Because water suitable for reuse is often a
by-product of existing secondary and tertiary
wastewater treatment processes, this type of water
recycling is a low-energy source of water supply.
This is especially true in areas like Southern
California, where enormous amounts of energy
are required to import water. Recycled water
can be delivered to users, usually at less cost
than non-recycled water, for anything from
irrigating golf courses, parks, and crops, to
mixing concrete, to firefighting. In fact, Orange
County, California now uses advanced treatment
technologies to purify wastewater to beyond
bottled water quality, then allows it to percolate
into the groundwater basin for later use as
potable water. This system uses only about half
the energy that would be required to transport
that water from Northern California to Southern
California.