ENVIRONMENT AND ENERGY
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the materials recovered. The water may be recycled within
a plant or by another linked industry, or it may be simply
discharged, returning it to the hydrological cycle for others to
use. In the USA, it has been estimated that for some major
rivers the water has been used and reused over 20 times
before it reaches the sea (TSG, 2014). Useful materials may
be recovered, such as minerals (phosphates) and metals.
Cooling water may provide heat. Residual sludge might yield
biogas or may have no other fate than disposal.
Table 6.4: Content of typical wastewater in some major industries
ADDRESSING THE RESOURCE CHALLENGE
If wastewater is accepted as a positive input, rather than an
unwanted output, of industrial activity demanding disposal,
there is a logical and preferred process from its elimination
to pro-active use and recycling.
REDUCING POLLUTION AND POLLUTION PREVENTION
As with many environmental issues, the first step is to
prevent or minimise pollution. The goal is to keep the
volumes and toxicity of pollution to a minimum at the point
of origin. This goes to the core of new green industrial
engineering, where the elimination of pollution and
wastewater is part of the equation from concept to design
for operations and maintenance.
However, with established plants, while some re-engineering
is possible, pollution reduction might be the only option. This
includes substitution with more environmentally friendly raw
materials and biodegradable process chemicals, as well
as staff education and training to identify pollution issues
and remedy them. By 2020, the market for industrial water
treatment technologies is predicted to grow by 50%.
REMOVING CONTAMINANTS
Industries discharging into municipal systems or surface water
have to comply with discharge by-laws or other regulations
to avoid fines, so in many cases end-of-pipe treatment is
required at the plant before release. In some situations,
industries find it also more economical to pay fines than to
invest in treatment to meet regulations (WWAP, 2015).
Mixed effluents require complex treatment trains and
result in one quality of wastewater discharge to meet local
regulations. This water, because it must often meet stringent
regulations, may be of unnecessarily higher quality than
required for other fates, such as recycling applications. As it
is usually more difficult and expensive to treat wastewater
containing many pollutants than wastewater with only one
such substance, stream separation is often desirable.
Mixing more concentrated wastewater with streams that might
be suitable for direct discharge or recycling should also be
avoided (WWAP, 2006). However, in certain specific cases,
appropriate blending of wastewater streams from different
sources could potentially lead to beneficial effects in treatment.
www.plumbingafrica.co.za
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BOX 6.2: ANGLO AMERICAN eMALAHLENI WATER RECLAMATION PROJECT,
MPUMALANGA, SOUTH AFRICA
The Witbank coalfields are located around eMalahleni, a city of half a million
inhabitants in north-eastern South Africa. The region struggles with water scarcity
that is expected to become more severe in the future, while eMalahleni already has
difficulty in meeting the water demands of its rapidly expanding population.
The water reclamation initiative was started to ensure environmentally responsible
management of excess water in the mines, and a continuous supply of treated water
for mining activities, while eliminating the need to import water and the consequent
competition with other stakeholders for a scarce resource.
The eMalahleni Water Reclamation Plant treats water from the three Anglo American
thermal coal operations and uses desalination technology. Water from the mine is
converted to drinking water, process/industrial water and water that can be safely
released into the environment.
In the treatment process, gypsum is separated from the water and used as a
construction material. Some of this treated water is used directly in mining operations,
but the majority is for social use and meets 12% of eMalahleni’s daily water needs
offering a reliable and potable water supply.
Anglo American is minimising its water footprint and environmental impact while
delivering long-term benefits of safe and uninterrupted access to coal reserves from
operating mines and eliminating both the need to import water and the uncontrolled
release of water from participating mines.
Source: Adapted from WBCSD/IWA (n.d.)
November 2018 Volume 24 I Number 9