Canadian Finishing & Coatings Manufacturing Magazine Jan/Feb 2023 - 58

PLATING AND ANODIZING: WASTEWATER TECHNOLOGY
nickel sulfamate bath, " says Chan. " Fortunately the company was
running a prototype line so there was wastewater being produced
to experiment with and we jointly developed a treatment
protocol. We are still using the conventional phys-chem
precipitation style of system with a pH adjustment and chemical
additives and inclined plate clarifiers to separate the solids from
the wastewater. "
Chan continues, " But because of the unique nature of this type
of wastewater we had to do a two-stage treatment, with each
stage targeting the removal of the three metals. "
Additionally, Kontek is also considering ion exchange resins
for use in removing either boron, selenium or cobalt, as these
metals and their related metal complexes are challenging to
remove or separate from wastewater via precipitation. Even with
IX technology, there is a requirement to eventually evaporate the
IX regenerant wastewater since this is where the removed metals
will be concentrated.
But again, for Kontek it's about finding the right technology or
a mix of technologies to meet the unique needs of customers as
it's all about what's in the solution to begin with and it's facility
specific.
" Our systems have anywhere from four to eight different
technologies. And once you integrate them all together, then that
becomes the system, " says Chan.
" With our sister company Moonstone, we are using different
bentonite clay based additives to encapsulate the contaminants,
which can then be filtered to remove said contaminants from
the wastewater. Traditionally these units had a niche market in
terms of oily wastewaters, spent coolant with emulsified oils or
fluorescent penetrant indicator (FPI) rinse waters. A Moonstone
unit, when compared to a Kontek system with a comparable flow
rate, requires a lot less physical space, and is also much more cost
effective.
Chan says that they recently tested water samples from a local
anodizing shop and did treatment studies on all their individual
process solutions and their rinse water. And in all cases, the
Moonstone unit performed very well.
" We are yet to go to the next step of doing an analysis on the
treated water partly because with anodizing rinse water-at this
location-it would be aluminum. And with aluminum having
a high discharge limit (typically 30-50 ppm), I'm 100 per cent
sure that our treated rinse water sample is well below the limit, "
says Chan. " We're always looking at what other waste streams
Moonstone can treat efficiently. Last year we sold many of these
units to a company that manufactures anodizing or plating lines.
It's a smaller, modular type of standalone treatment system with
a lower capital cost, that in many cases will allow the customer to
comply with their discharge regulations. "
Although plating and anodizing operations don't particularly
enjoy dealing with wastewater or may not consider it a priority
until a fine is in place or there's increased regulatory pressures,
there are a variety of solutions that can help drive down the
capital cost of such an investment. It all comes down to risk
mitigation. And while there are those striving for ZLD, Kontek
has noticed more companies being more realistic with their
waste minimization targets, and opting for MLD instead.
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H20's VACUDEST:
How it works
H20's VACUDEST is a vacuum distillation
technology that offers a physical evaporation
process that separates surfactants, heavy metals,
acids and alkalis from wastewater with a focus on
the reuse of recovered water.
The company says that direct vapour compression
evaporators have been developed to reduce energy
consumption during the evaporation process (the
separation of water and contaminants through
a difference in boiling point). An under-pressure
of about 600 mbars is created using a roots
compressor, working contact free in the evaporator.
Due to the low pressure, water evaporates at
temperatures around 86°C. The steam created
by the evaporation is compressed to atmospheric
pressure by the vacuum pump. Since the relation
of temperature to pressure is constant (under ideal
circumstances) the temperature of the steam will
rise when the pressure increases. The hot steam
will then be fed to a heat exchanger. The steam,
which is just above 100°C, will condensate in the
heat exchanger.
The condensation energy is used to evaporate the
wastewater being fed into the system; therefore
no external heating systems are required. The
condensation energy of the steam is sufficient to
heat and evaporate the wastewater. The only energy
consumer in the evaporator is the vacuum pump,
using about 45 - 60 Wh/l. This energy consumption
is by five times lower compared to heat pump
systems.
" Due to the energy recycling, the required energy is
about 45-75 kWh/m³, depending on the size of the
equipment due to economy of scales, " says Marius
Straub, project engineer for H20. " Compared
to atmospheric evaporation system, which has
an energy consumption of ~750 kWh/m³, the
VACUDEST saves up to 95 per cent of the energy. "
For plating and anodizing operations, Straub says
that the key benefits include:
* Low running costs: about 10-15 USD/m³
including energy, labour, spare parts, and
consumables.
* Recycling: In the majority of the applications
the distillate quality is good enough to reuse the
distillate directly or after polishing (e.g. IEX unit)
in the process again.
* Easy handling: The unit is ready for industry 4.0
and its fully automatic operation offers a very low
allocation of human resources (two-four h/week).
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