HEALTH AND SANITATION
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the system as it experiences temperature, pressure, and
oxygen changes.
E. coli served as an indicator organism of microbial
activity, with the results of this study showing a wide
range of E. coli concentrations that may be related
to household size and the inputs at each source (for
example one household included their kitchen basin as
a source of greywater). The qualitative analysis indicated
that in some instances, greywater could pose a risk to
human health, soils, and the environment.
An example of this is that many users do not switch off
their system during periods of high rainfall and saturated
conditions, resulting in some pooling of greywater in their
garden. The results showed that, whilst most respondents
were successfully using their greywater and did not report
problems with the systems, many residents do not follow
some of the basic rules regarding handling of greywater
(for example switching off the system during periods of
rainfall) — and could thus be exposing themselves to
various levels of risk.
This reaffirms the difficulties in quantifying and qualifying
greywater risk to humans, soils, and the ecology of the
environment. However, assessing the use and management
of greywater in a private space that is managed by purpose-
built technologies, identifies how these risks are being
managed within domestic households. The study therefore
provides another snapshot into considerations for guidelines
towards safer and sustainable use of domestic greywater.
USES FOR WHICH GREYWATER IS INAPPROPRIATE
Specific guidance in respect of greywater use will be
provided in another future article, but the general rule is
that greywater should never be used in any manner where
it may easily come into contact with susceptible individuals
and/or ingested. Therefore, it is totally inappropriate for use
in the following situations:
• Drinking or cooking.
• Irrigating of any produce eaten raw or minimally
processed, such as leafy produce or root vegetables
(for example carrots and beetroot) growing in soil
frequently irrigated with greywater.
• Washing / cleaning pavements — especially those
draining to stormwater systems.
• Irrigating gardens during or immediately subsequent
to rainfall.
• Irrigating areas in gardens such as lawns where
children play. Children are the group most susceptible
to picking up infections from greywater. PA
In the following article, we look at the management of
greywater in un-serviced settlements.
November 2018 Volume 24 I Number 9