HEALTH AND SANITATION
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landscape irrigation; as well as for a number of household purposes,
such as toilet flushing and cleaning of pathways. The Water Research
Commission says recent research is also considering the use of grey
water to maintain 'green walls' (and thereby contributing to urban
cooling) associated with large commercial/residential developments.
The WRC suggests: “There remains little in the way of published local
guidance as to how grey water systems should be designed, operated,
and maintained as part of an integrated water supply system. This
project was thus aimed at providing the necessary guidance to support
the wider adoption of domestic grey water management and use in
South Africa to support the continued integration of the management of
the urban water cycle.
“The management and use of grey water can pose significant risks,
specifically in terms of the potential health and environmental hazards
from chemical and microbiological contaminants and disease vectors,
depending on the source of the grey water (for example, serviced or
unserviced settlements), the treatment process adopted (if any), and the
use for which it is intended. Grey water quality is highly variable, and
there is a need to develop guidelines to ensure the safe management and
use of grey water as an alternate water resource, and also to limit and
manage inappropriate disposal in areas where it has the potential to result
in major health hazards; specifically, in low-income/ ‘gap’ housing and
informal settlements.”
Many buildings are today being designed according to LEED standards
(see this month’s project, the Deloitte building on page 26), and the
Green Building Alliance which manages LEED says the programme
offers projects that obtain the necessary permits, the collection and
use of greywater can contribute to several LEED credits in the Water
Efficiency (WE) category:
• WE Credit 1: Water Efficient Landscaping (2-4 points)
• WE Credit 2: Innovative Wastewater Technologies (2 points)
• WE Credit 3: Water Use Reduction (2-4 points)
It also offers the following pointers: “For all types of greywater reuse, the
following guidelines apply:
• Minimise contact with it
• Never store untreated greywater for more than 24 hours as the organic
material it contains will rapidly decompose, causing it to become more
hazardous and unpleasant smelling
• When irrigating, do not allow it to pool
• Don’t use greywater to irrigate edible root plants; and
• Label any pipes carrying greywater as ‘Non-Potable Water – Do
Not Drink’ and label valves to show where the water
is going.
“When irrigating with grey water, lines should be buried a few inches
under the ground’s surface and each outlet should direct water into
a mulch basin protected with a mulch shield. For subsurface drip
irrigation, conventional drip tubing cannot be used unless water is filtered
thoroughly! Emitters designed for greywater are much less likely to get
clogged.” PA
References:
1. Water Research Commission
2. Burgess Plumbing
August 2020 Volume 26 I Number 06