Since only a fraction of potable water supplied is used for drinking and cooking, it makes sense to use recycled water for other "Non Potable" demands, such as toilet flushing, irrigation of the land-scapes, etc.
Grey water use to be considered to be from hand wash basins, baths, showers and kitchens but the inclusion of kitchen waste water makes Grey Water Treatment very complicated due to the fats, oil and greases and high BOD load. This is Dark Grey water.
If the kitchen water is discharged to the sewer with the toilet water, then the grey water (the Light Grey water) can easily be treated back to near potable quality using a simple process of ozone dosing, Ultra Filtration and chlorination for residual disinfection.
With a simple and compact process, a very significant amount of grey water can be recycled back to domestic use.
