Household Utilities: Grey Water: Defining Grey Water.

Greywater is the used water from bathrooms, sinks, kitchen and the laundry. It may contain soap, detergents and cooking residue, but does not contain faeces or urine.

Greywater comprises 52% of the average household's used water. If the average middle wage earner uses 180 litres of water per day, then 93.6 litres per day could be greywater.

When appropriately treated, greywater can be recycled and used for toilet flushing, in the laundry and for watering the garden (depending on local council rulings). Greywater provides an excellent water and energy conservation strategy.

Greywater should not be stored, as it will rapidly develop an offensive sulphurous anaerobic smell. It should be regarded as polluted water as pathogens are potentially present. Grease traps in the kitchen and lint traps from the laundry will reduce the amount of solid content, thus minimising the possibility of blocked pipes. Tanks, filters and pumps are best avoided, as the need for maintenance increases the risk of the design being less than optimally implemented.

If greywater is to be recycled into the garden, then the potential for pollution or contamination from the greywater needs to be addressed. If greywater is being used to grow vegetables for human consumption, the edible portion of the fruit or vegetable should not come in direct contact with the greywater. This can be prevented by using greywater on fruiting trees or vegetable, ensuring that there is a thick layer of mulch between the soil and plant. The greywater being recycled is best incorporated into a sensitive garden design, with reduced lawn areas and home food production areas.

Laundry powders contain elements that can impact on the garden:

1. Sodium affects soil permeability.

2. Boron and high phosphate levels in detergents may affect native plants.

3. Non-chlorine bleaches is preferred, as this will have a less deleterious effect.

The current standard for garden surface irrigation is chlorinated effluent containing no more then 20mg/L BOD and 30mg/L suspended solids.

Greywater Planning

The design of a greywater system must consider:

1. location in relation to the dwelling,

2. location of existing structures,

3. site slope,

4. soil classification and percolation test results,

5. potential for impact on sub-surface potable water supplies,

6. ground water level,

7. domestic water sources on site or in neighbouring properties,

8. location of greywater irrigation pipes,

9. management of all greywater production from the household,

10. restricted to the consumers land, and

11. prevention of storm runoff entering the disposal area.

LINKS

http://www.env.qld.gov.au/environment/environment/water/

http://www.sustainable.com.au/greywater.html

http://farrer.riv.csu.edu.au/ASGAP/APOL22/jun01-5.html Australian Plants Online

http://www.cahe.nmsu.edu/pubs/_m/m-106.html Safe Use of Grey Water