HEALTH AND SANITATION
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There are also basic handling rules to be followed
when disposing or reusing greywater (for example,
using eco-friendly / ‘natural’ / biocompatible cleaning
products, and limiting storage time before use). The
economic viability of greywater harvesting systems
is a key consideration; for example, Ilemobade et
al. (2012) suggest a maximum payback period of
eight years for greywater reuse for toilet flushing.
Consideration of any legislative (e.g. municipal by-
laws) or policy requirements and the linkages to other
water services (e.g. sewerage or irrigation systems)
is also important when designing a greywater system
— particularly in respect of their potential impact on
these systems.
Considering the lack of any code of practice for the use
of greywater in South Africa, it is useful to summarise
the main ‘dos and don’ts’ in the regulations used by the
world leaders in greywater reuse, for example: Australia
(State of Victoria, 2004), Jordan (CSBE, 2003), and the
United States of America (Water Conservation Alliance of
Southern Arizona, 2003), as follows:
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Avoid direct human contact with greywater, or soil
irrigated with greywater.
Water that comes into contact with a toilet, urinal or
a toilet fixture such as a bidet should never be used
as greywater.
Water that has been used to wash nappies or other
clothing soiled by faeces and/or urine should not
be used; nor should that generated by cleaning in
the laundry or bathroom, or when using hair dye or
other chemicals.
Water from the kitchen sink or used in the kitchen
to wash dishes or food should not be used (it is too
highly contaminated with grease, bacteria, blood,
and chemicals). Also, do not use greywater that is
generated by washing cloths / brushes used for
painting or for maintaining machinery and vehicles.
Preferably use only ‘low risk’ greywater — e.g.
warm-up water from hot taps, rinse water, bath or
shower water.
Store warm water in a holding tank to cool down and
use within 24 hours; otherwise the bacterial load will
rise too high for safety. This tank should be classified
as a septic tank and all the regulations for septic tanks
should apply to such a system. Water stored for longer
than 24 hours should be treated before use, especially
if applied to garden areas where humans and animals
can come into contact with such water.
Greywater should never be applied to uncooked
edible crops — such as vegetables eaten raw or
lightly cooked, such as in salads. It should also be
avoided for root crops such as carrots, since the
pathogens can accumulate in the topsoil.
www.plumbingafrica.co.za
Greywater offers
great potential for
improvement in
household nutritional
status and social
functioning in poor rural
settlements.
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Care should be taken to ensure greywater never
comes in contact with the produce being irrigated.
This may be achieved through drip irrigation,
subsurface irrigation, or irrigation under a heavy
mulch cover.
Greywater should only be used in locations where
groundwater is at least five feet (approximately
1.5m) below the surface.
Surface accumulation of greywater must be kept
to a minimum. Care should be taken to ensure
greywater does not run off irrigated surfaces into
water courses, stormwater drains, swimming pools
or dams.
Greywater should not be allowed to leave the
boundaries of the property. Excess greywater
should be disposed of into the sewerage system
during rain periods or when too much greywater is
produced for the garden to absorb.
Children and pets should be kept away from areas
that are irrigated with greywater. Children are the
highest risk group for acquiring infection from
greywater.
Encourage every person living on the premises
where gardens are irrigated with greywater to wash
their hands without fail before eating or drinking.
Label pipes carrying greywater under pressure, to
eliminate confusion between greywater and potable
(drinking) water pipes.
Greywater should never be allowed to pond or
pool where mosquitoes and other insect vectors of
disease can breed.
Water used to wash animals such as domestic
pets should not be used — it typically has high
concentrations of organisms able to cause disease.
Greywater should not be used if anybody living on
the premises is suffering from diarrhoea, ear or
skin infections.
Never use hosing, spraying or misting methods
when irrigating with greywater. PA
In the following article, we look at greywater harvesting
techniques.
January 2019 Volume 25 I Number 1