Greywater

Greywater (also spelled graywater, grey water or gray water) refers to all domestic wastewater produced, excluding sewage. The main difference between greywater and sewage or blackwater is the organic loading. Greywater comes from sources like sinks, showers, baths, washing machines, and dishwashers. As such, it contains fewer pathogens than blackwater and can be recycled on-site for uses such as landscape irrigation and constructed wetlands. Greywater recycling not only reduces the demand on the freshwater supply but also minimizes the volume of wastewater entering sewage treatment facilities.

Sources and Composition

Greywater typically includes water from:

• Bathroom sinks
• Showers
• Bathtubs
• Washing machines
• Dishwashers

The composition of greywater can vary significantly depending on the source and household habits. It generally contains traces of dirt, food, grease, hair, and certain household cleaning products. While greywater may look "dirty," it is a valuable resource that, when treated properly, can be reused for non-potable purposes.

Treatment and Reuse

The treatment of greywater can range from simple systems that filter and divert water for toilet flushing or garden irrigation to more complex systems involving biological and mechanical filtration for reuse in domestic applications. The choice of treatment system depends on the intended reuse application, local regulations, and the quality of greywater. Common reuse applications include:

• Irrigation for gardens and landscapes
• Toilet flushing
• Laundry washing

Regulations

Regulations regarding the treatment and reuse of greywater vary widely by region and country. It is essential to consult local guidelines and obtain necessary permits before installing a greywater recycling system.

Benefits

The benefits of greywater recycling include:

• Reduced use of freshwater
• Decreased demand on municipal sewage treatment facilities
• Lower water bills
• Enhanced plant growth from nutrients in greywater
• Increased awareness and appreciation of water as a resource

Risks

Improper treatment and use of greywater can pose health risks, particularly if pathogens are not adequately removed. It is crucial to ensure that greywater systems are designed and maintained correctly to avoid contact with untreated greywater.

See Also

• Water conservation
• Sustainable living
• Wastewater treatment
• Constructed wetland