What is Greywater? Why use Greywater?
-
What is Greywater?
-
What is Blackwater?
-
What is Wastewater?
-
Why use Greywater?
-
Benefits of using Greywater
-
Perth water supply & Perth climate change
WHAT IS GREYWATER?
Greywater is domestic wastewater from:
- baths
- showers
- spas
- bathroom basins
- washing machines
- laundry tubs
- kitchens
Kitchen greywater must be treated before use as it can contain elevated levels of greases, oil and detergents (Department of Health, 2010; DWER, 2019).
Greywater can be diverted to the garden via simple low-cost technology to provide an alternative water source to reduce scheme water demand and meet garden irrigation requirements, particularly in summer when Perth water restrictions are in force.
With treatment, greywater can also be used for flushing toilets and washing clothes.
WHAT IS BLACKWATER?
Blackwater is the wastewater from toilets, urinals or bidets.
WHAT IS WASTEWATER?
Wastewater is both greywater and blackwater.
WHY USE GREY WATER?
Greywater reuse can help meet the water requirements of gardens without placing additional demand on scheme water and can help keep gardens green when Perth water restrictions are in place. This is important, as currently around 40% of all residential scheme water is used for garden irrigation. Greywater resources are not being fully utilised due to a lack of knowledge and understanding.
- HOW MUCH WATER IS USED IN THE GARDEN? 40%
- HOW MUCH WATER IS USED IN THE HOME? 60%
BENEFITS OF USING GREYWATER INCLUDE:
Scheme water savings
Greywater reuse cuts the amount of scheme water used for irrigation of gardens and lawns, reducing pressure on this supply. Water savings will vary depending on the volume of greywater generated, the type of reuse system, garden water demand and maintenance.
Additional nutrients for plants
The nutrient content of greywater, primarily nitrogen and phosphorus , benefits many garden plants growing in Western Australia’s nutrient poor soils.
Restriction-free water supply
Typically, a consistent amount of water is used in homes for showering and laundry each day. Reusing this water can provide a regular supply of irrigation water for gardens and lawns that is not limited by water restrictions, resulting in greener gardens and landscapes.
Lemon tree thriving on greywater
Macadamia trees with greywater dripline
Creating cool and green neighbourhoods
A consistent supply of greywater for irrigation helps to green and cool our neighbourhoods. One unfortunate response to reduce scheme water use has been to replace lawns and gardens with paving and artificial turf making our neighbourhoods hotter, harder and less biodiverse.
Achieving targets for increased wastewater recycling in WA
A combination of water efficiency measures, development of new water sources and increasing the amount of wastewater recycled is required to ensure Perth’s water supply is resilient and used wisely.
Wastewater recycling, including greywater reuse, is currently around 10% in the Perth metropolitan area (AWA, 2018).
There is an ambitious State target to increase wastewater recycling to 30% by 2030 (Water Corporation, 2019) and greywater reuse can play its part in achieving these targets, alongside larger reuse schemes.
Saves energy and greenhouse gas emission – Reduction of wastewater volumes
Water used in bathrooms and laundries that goes ‘down the drain’ is currently mixed with toilet water and must undergo significant treatment to be purified before being discharged into the environment.
Using greywater where it is produced reduces the amount of wastewater that needs to be treated via wastewater treatment plants, saving energy (and greenhouse gas emissions) through reduced pumping and processing.
Perth water supply & Perth climate change
Perth’s average rainfall has been falling steadily since the mid-1970s because of our changing climate.
Simultaneously, run off into Perth’s dams has fallen by more than half and there is compelling evidence that this drying and warming shift will continue to worsen (BOM and CSIRO, 2018).
Combined with continued population growth, there is increasing pressure on our valuable drinking water sources, making them more expensive and energy intensive as we become almost entirely reliant on water supplied from deeper underground aquifers and desalination.
WA's Estimated Population in 2031
WA'S ESTIMATED POPULATION IN 2061
Around 70% of total scheme water use in Perth is residential, with the average household using approximately 277,000 litres per year (Water Corporation, 2010).
Approximately 40% of all residential water use is for watering lawns and gardens (Water Corporation, 2010).
- 70% of scheme water in Perth is for residentialuse 70%
- 40% of all residential water use is for watering lawns and gardens 40%
Alternative, fit-for-purpose water sources, such as greywater, need to be considered to alleviate the pressure on scheme water and still meet Perth resident’s preferences for green gardens and cool neighbourhoods.
The average household in Perth uses approximately 277,000 litres per year
References:
Australian Water Association (2018). Water Corporation expands Perth wastewater treatment plant capacity. Water Source. https://watersource.awa.asn.au/business/assets-and-operations/water-corporation-expands-perth-wastewater-treatment-plant-capacity/ (Accessed 26/3/2019).
Bureau of Meteorology (BOM) and Commonwealth Scientific and Industrial Research Organisation (CSIRO) (2018). State of the Climate 2018.
Department of Health (2010). Code of Practice for the Reuse of Greywater in Western Australia. https://ww2.health.wa.gov.au/~/media/Files/Corporate/general%20documents/water/Wastewater/COP-Greywater-Reuse-2010.pdf (Accessed 22/1/2019).
Department of Water and Environmental Regulation (2019). Greywater. http://www.water.wa.gov.au/urban-water/water-recycling-efficiencies/waterwise-community-toolkit/greywater (Accessed 22/1/2019).
Water Corporation (2010). Perth Residential Water Use Study 2008-2009.
Water Corporation (2019). Recycled Water. https://www.watercorporation.com.au/water-supply/our-water-sources/recycled-water (Accessed 23/1/2019).
