you are considering using wastewater from your home, there are
environmental and health issues associated with this practice which
can be managed. The following information outlines `best management
practices' when using greywater. Domestic greywater is household
wastewater, which has not come into contact with toilet waste. It
includes wastewater from bathtubs, showers, bathroom wash basins,
washing machines, laundry tubs and kitchen sinks.
contains chemical pollutants that primarily come from household
detergents and cleansers. Some chemicals present in greywater may be
valuable fertiliser for lawn and garden watering. However, others may
be harmful to vegetation and soils. These include sodium, total
salts, chloride and boron. Untreated greywater from kitchen sinks,
dishwashers and garbage disposal units should not be used for
irrigation. Products can be chosen which contain none or reduced
amounts of harmful chemicals. Water softeners and certain powdered
detergents can contain sodium salts in high concentrations. Liquid
laundry detergents generally contain lower concentrations of salts.
all greywater has the potential to cause disease, the danger varies
considerably between households and between sources of greywater. For
example, the risk of disease is generally lower in greywater from
families without children compared with greywater from families with
children. Laundry water from soiled nappies or wash water from
domestic animals should not be used.
is some evidence to suggest that background levels of disease causing
organisms in the soil are often higher than from greywater used for
irrigation. Greywater is also naturally purified by the biological
activity in the topsoil.
TO USE GREYWATER
potential health risks associated with greywater irrigation depends
on the source of the greywater and the way it is applied. For
instance, if greywater is applied in the top 300 mm of soil through
sub surface irrigation, disease causing organisms are less
likely to survive than with surface application.
should not come into contact with the edible portion of fruit or
vegetables. During long periods of dry weather, greywater irrigated
areas should be irrigated periodically with normal or tank water to
prevent salt building up in the soil.
legislation requires that greywater reuse be kept within the boundary
of the property from which it is produced. Overflows, including that
from a greywater surge tank, must not be allowed to leave the
property or enter the stormwater system. Avoid greywater use when the
soil is wet or rain is imminent. Guide for permeable surface area
m2 is required for laundry wastewater only
m2 is required for bathroom wastewater only
low evaporation in the ACT during May to August limits irrigation to
the other months.
of greywater promotes the generation of offensive odours and the
growth of microorganisms. Direct reuse is preferred. A surge
tank may be installed between the plumbing fixtures sourcing the
greywater and the reuse area on all greywater reuse systems. The
surge tank should not contain a surge volume greater than 80 litres.
An overflow drain should be provided at the top water level and
should have a permanent connection to sewer.
aware of the likelihood of blockages in irrigation pipework caused by
the accumulation of oils, grease and bacterial slime. This may be
avoided by using pressurised systems. Household plumbing should be
carried out by a licensed plumber in accordance with Australian
Standards AS 3500 and AS 1345.