Greywater makes up about 65% of the total wastewater produced by an average household and is a good source of water for reuse. Greywater is all wastewater generated in households or office buildings from hand wash basins, showers, baths and clothes washing machines. It does not include kitchen sinks, dishwashers, toilets, urinals and bidets. Domestic greywater can be recycled directly within the home, garden or company and used either immediately or processed and stored. If stored, it must be used within a short time or it will begin to putrefy due to the organic solids in the water. Recycled greywater of this kind is never safe to drink, but a number of treatment steps can be used to provide water for washing, flushing toilets and irrigation.
The application of greywater recycling provides substantial benefits for both the water supply system as well as the wastewater treatment system.
The treatment process, from biological systems such as wetlands and bioreactors or more compact systems such as membrane bioreactors or mechanical systems eg sand filtration and UV radiation, depends on the end application.
Some greywater recycling benefits:
- Reduces freshwater extraction from rivers and aquifers
- Reduces pressure on wastewater treatment plants
- Reduces energy use and chemical pollution from treatment