HEALTH AND SANITATION
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Regarding the use of grey water for domestic irrigation, one
of the most useful studies in this regard was undertaken on
a selected range of bathroom products (solid soaps, liquid
body washes, shampoos and hair conditioners) to assess their
potential impacts on soil chemistry and structure when they are
present in grey water. •
Whilst it was found that the effects of grey water on soil vary
depending on the type of soil present, many general observations
were made on the basis of the results of chemical testing
obtained for the simulated grey water generated by each product:
• Most hard soaps produced high pH grey water, which over
time could be damaging to plants and soil. The electrical
conductivity (EC) levels of this grey water are unlikely to
pose long-term problems associated with induced salinity.
However, the sodium level of all products tested was very
high and poses a ‘sodium hazard’ to clay soils over time
— this is supported by the soil stability results obtained
in this study, which showed that most of the hard soaps
caused extensive dispersion of all the soils tested.
• The sodium level of most shampoos, conditioners and body
washes was low although the long-term effects of some
of the shampoos would need to be investigated further as
low sodium content grey water can still cause long-term
problems if the levels of other cations such as calcium and
magnesium are low. •
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The levels of potassium found for most products would appear
to provide a source of potassic fertiliser and not pose any
long-term problems associated with nutrient build-up.
The levels of zinc in some hard soaps could pose long term
problems of zinc accumulation in the receiving soil.
Most of the products tested produced grey water with low
phosphorus levels.
There was no indication that so called ‘eco-friendly’ products
were more suitable for grey water irrigation systems than
mainstream products, possibly due to the increased use of
sodium chloride salt in many of these products.
The effects of these and other constituents such as
emulsifiers, preservatives, microbeads, etc. in personal care
products have not been evaluated in local (South African)
soils and under local weather conditions. Grey water from
bathrooms also potentially contains products such as
medicines, disinfectants, pesticides, dyes, clothes detergents
and fabric softeners. The presence and concentrations of
these pollutants vary according to the habits of the occupants
of the house and the alternative disposal systems available
to them. The choice of bathroom products for use in grey
water irrigation systems is thus critical to prevent the long-
term chemical and structural deterioration of receiving soils.
Products with high sodium levels should be avoided due to
their destructive effects on clay soils. PA
July 2018 Volume 24 I Number 5