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UNIT 4: ENVIRONMENT MANAGEMENT SYSTEMS
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some chemical impurities. Ozone can be created through:
• The UV, or photochemical method, which passes air through UV lamps,
the UV rays turning the oxygen molecules into ozone, just as in the
stratosphere;
• High-voltage electricity being passed through dry air in a vacuum.
The ozone obtained is then introduced into the water via a compressor or similar
device.
Also gaining ground is pool water purification by UVC radiation lamps, which
radiate UV energy at 240-280 nanometres per second. The light is absorbed by
the DNA of bacteria, moulds, viruses and yeast, which then leads to a change in
the genetic material so that they are no longer able to multiply. Some chlorine
(about 10% of conventional quantities) is then needed to provide residual bacterial
control. A second benefit of this method is that UVC light has a photochemical
effect, which can destroy chloramines 2 and other by-products of chlorine. ‘Free’
chlorine is then released back into the water to perform its intended task of
disinfection. Not only are water quality and atmospheric conditions considerably
improved, but also much less chlorine has to be added to provide the residual
bacterial control.
Monitoring Water Consumption
Since water is directly linked to the level of occupancy/activity, it is best to monitor
and benchmark water use on the basis of guest nights or visitor numbers.
Water meters are essential for the monitoring of water use. Different areas of the
business could be sub-metered for the collection of more specific data. Comparing
water use over the years and benchmarking with other facilities of similar size
and standing can provide valuable information for improved water management
and increased savings on water and energy costs. When benchmarking with other
properties it must be remembered that water use will vary greatly depending on
the size of the property, services offered, level of activity and climatic conditions.
It is good environment and business practice to collect and reuse rainwater for
irrigation and other non-drinking uses. Water collection tanks can be installed on
the roof or at ground level. If the water is to be used in-house it may require a
minimum level of treatment. The collection and use of rainwater is discussed in
more detail in Unit 5.
It is possible to supplement non-drinking water needs by treating and reusing
wastewater. The first consideration in wastewater reuse is to distinguish between
‘grey’ and ‘black’ water. Grey water is wastewater from bathrooms, laundries and
kitchens; black water is wastewater from toilets. Black water contains pathogens
and almost ten times more nitrogen than grey water, and therefore needs to go
through a two- or three-stage biological treatment process before it can be reused.
Grey water treatment is less intensive and can be safely conducted on-site. The
treated water can be used for irrigation, toilet flushing and other non-drinking
uses.
Over the last ten years, many national water supply and plumbing regulations
have been modified to accommodate the reuse of grey water. They are most easily
incorporated in the initial design process of a building, as separate drains and
septic tanks have to be built. In the case of existing buildings, retrofitting drainage
2
When chlorine and ammonia
are both present in water,
they react to form ‘combined
chlorine’ products called
chloramines. They are less
effective disinfectants than
‘free’ chlorine.
Since water is
2 directly linked to
the level of
occupancy/
activity, it is best
to monitor and
Reuse of Treated Wastewater
benchmark water
use on the basis
of guest nights or
visitor numbers.