CARBON ZERO MANUFACTURING
THE ROLE OF ZERO
LIQUID DISCHARGE
IN REDUCING HAZARDOUS WASTES
Thanks to tighter
environmental regulations
and greater public
awareness, companies
are increasingly looking
to reduce or eliminate the waste
that they produce. In recent
years, Zero Liquid Discharge
(ZLD) has become an important
waste reduction technique,
but its potential in dealing with
hazardous waste streams has not
been fully appreciated until now.
Hazardous waste is waste which
is dangerous or potentially
harmful to the environment or
human health. It can come in any
form: solid, gaseous, sludge or
liquid. Many vital materials such
as cleaning products, pesticides
and industrial chemicals are,
by their nature, hazardous and
therefore present disposal
challenges.
Traditionally, hazardous wastes
have been treated by a number
of different physical, thermal,
chemical and biological methods,
including precipitation, high
temperature incineration and
even burial in specialist secure
sites. However, in parts of the
world, particular industries
have become associated with
environmental pollution through
the inappropriate disposal of
hazardous wastes, with the
textiles industry in India and
South East Asia being such
an example; one which has
attracted NGO interest and the
development of new cleaner
waste disposal schemes.
One of the advantages of ZLD
over other treatment techniques
is its theoretical ability to
separate unwanted materials from
water, whether they are benign,
hazardous or toxic. The resulting
solid residue is often more stable,
making it suitable for recycling
or landfill. A well-designed ZLD
system should minimise or even
eliminate liquid waste streams,
resulting in clean water for reuse
or environmentally-friendly
discharge, and a solid residue
suitable for further processing
(often to recover valuable
components for use elsewhere)
or for safe disposal.
Correct analysis is crucial
The composition of wastewater
streams varies greatly, even
where the same basic processes
are involved. Certain wastewater
sources, such as power plants
HRS Unicus Series scraped-surface evaporators are used
to maintain thermal efficiency and remove fouling during
evaporation in ZLD installations
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