ENVIRONMENT AND ENERGY
33
Box 6.3: Creative use of wastewater at Carbery Milk Products in Cork, Ireland.
Bioethanol
Either way, fit-for-purpose treatment can
optimize the water quality for its next role.
There exists a myriad of possible treatment
options, including stabilisation ponds, anaerobic
digestion and bioreactors to produce biogas,
activated sludge, different types of membranes,
UV radiation, ozonation, advanced oxidation
and the use of wetlands of various sorts.
In 2015, the oil and gas, food and beverage,
and mining industries were expected to
account for over half of all expenditures on
wastewater treatment technologies, and
further growth in technology was anticipated
for meeting strict discharge requirements,
for example in the mining sector
(see Box 6.2). By 2020, the market for
industrial water treatment technologies is
predicted to grow by 50% (GWI, 2015).
RECYCLING WASTEWATER AND
RECOVERING BY-PRODUCTS
Recycling within a plant
Overall, industry is in a good position to use
or recycle its wastewater internally. This
might involve the direct use of untreated
wastewater, provided its quality is good
enough for the intended purpose.
Cooling and heating water, as well as
rainwater, may be suitable for washing, pH
adjustment and fire protection. However,
process water which is sufficiently treated to
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match resulting quality with intended purpose
has more potential for recycling, for example in
conveying materials, rinse water, water-cooling
towers, boiler feed, production line needs, dust
suppression, and washing (see Box 6.3).
This quality is accomplished by decentralised
treatment systems. While the technology is
generally available, as noted in Box 6.2, and
there is a trend to reduce the gap between
treatment and recycling (GE Reports, 2015),
obstacles may include implementation, costs
not outweighing benefits, long payback
periods, maintenance and increased energy
consumption. Moreover, the location and
availability (intermittent, batch or continuous
production) of the wastewater stream must fit
with its intended use.
Using wastewater or recycling treated
wastewater is a process that can be repeated
many times. It not only reduces the cost for
industry of acquiring freshwater by decreasing
intake, particularly in areas or times of scarcity,
but also has the added benefit of reducing
discharges. In this way, the need to meet
regulatory standards and the risk of fines is
minimised. Furthermore, the practice benefits
the environment and adds weight to any social
license to operate.
Look out for Part 2 of the report in the
January 2019 issue of Plumbing Africa. PA
November 2018 Volume 24 I Number 9