As my grandfather would tell you, “There’s nothing wrong with skim milk that a little
half and half won’t fix.” A point made in a joke, that a little of the right chemistry
can go a long way.
In the manufacturing world the focus is constantly on
production and the speed with which parts are processed and
sold. The primary goal, to get parts out the door efficiently
while reducing both the time to market and the cost of
manufacturing, rarely considers the waste treatment process.
This makes waste treatment a fertile source of improvements in
efficiencies that can simultaneously increase both the bottom
line and environmental impact. This article will touch on
several ways that your waste treatment process can benefit from
a review and update in technology to first, reduce the process
inputs, including time commitment, chemical consumption,
monetary spend and oversight. And second, provide the
added benefit of reducing the amount of sludge and regulated
effluents on the output side.
Minimizing the Impact
Waste streams are often complicated mixtures from multiple
sources. Coming from the desire to get a better powder coating
through phosphating and cleaning, as well as associated
processes like stamping and metal removal, the waste stream
has a high degree of variability that requires a capable and
robust system to address the inputs from manufacturing and
meet the outputs required by municipalities.
When it comes to the treated waste, there is both a liquid
and a solid portion that can be optimized.
For solids - By reviewing the waste treatment process
and updating technologies, savings in terms of the amount of
sludge the process creates are possible. While this may seem
like a minor impact in the overall scheme of manufacturing,
the maintenance of press filters and the transport of sludge
to dumpsters take man hours that can be better applied to
getting parts through the production line and maintenance of
For liquids – The primary driver is meeting the levels
prescribed by the regulating authority. While this defines
the end, the means to that end is quite variable. Newer
polymer technologies introduced in coagulation have been
demonstrated to reduce the overall chemical usage and
therefore, expense. Equipment designed for processing and
delivering treatments can improve process efficiencies and
reduce chemical consumption.
The waste treatment process is governed by risk and a desire
to keep the company protected from bad PR as well as non-
Often sludge in waste treatment is considered a good
thing. You do, of course, want to remove the contaminants.
The production of sludge demonstrates that something
is happening, and that waste is being removed from the
solution. This view takes away from the end goal of removing
contaminants from the water to meet the requirements as
efficiently as possible.
For example, one manufacturer of cabs for agriculture
equipment had a long-standing process of treating their waste
water with calcium chloride and an anionic polymer to treat
the waste from their pretreatment and e-coat process. The
discharge met the city’s requirements for water pollutants. It
also was quite turbid and produced a large amount of sludge
that plugged up the filter press quite regularly. As is common
in manufacturing, the situation was endured for years in order
to produce parts. In fact, the situation went on so long that the
routine of monitoring and cleaning the filter press became part
of standard operations.
Updating technology can not only lead to cost savings,
it can result in process improvements and more time for
productive activities like making parts. In this case a review
of the process and effluent indicated that by upgrading the
technology from the classic calcium chloride and anionic
chemistries to the newer polyelectrolyte-flocculant and a high
performing polymerized coagulant, the process could deliver
three advantages. One benefit was environmental, an increase
in clarity. The second benefit was a 35 percent reduction in
sludge created at the filter press. The third benefit was achieved
by introducing a polymer blending system reducing the
amount of chemicals needed for the process.
Gaining Compliance: The Value of Process Review
Perhaps you have not been paying much attention to your
waste treatment process and are unaware of the state in which
it is currently operating. Such was the case for an agricultural
equipment supplier. It was observed that waste was lacking
clarity and the optimal pH for neutralization was not being
maintained. The process implemented traditional calcium
chloride technology and was being dosed excessively to meet
Testing for flocculation, the process by which fine particulates
are caused to clump together.
After a process review and testing was complete, the
company converted to a new polyelectrolyte and liquid
alum-polymer technology, which enabled them to achieve
the required clarity. In addition, the excessive use of calcium
chloride was eliminated, reducing sludge by 50 percent.
This case study clearly illustrates the value of process review
and its potential results in terms of reduced man-hours invested
in treating the waste as well as the amount of waste going to the
landfill. It is important to keep in mind that if you look solely
at the numbers related to chemical costs,
you may be overlooking potential savings
in time, waste disposal costs and avoiding
fines by complying with regulations.
By reviewing the waste treatment process
and updating technologies, savings in
terms of the amount of sludge the process
creates are possible
Lowering your Costs
Sustainability has become quite
a buzzword and as such, the costs of
sustainability are often overlooked or
muted. In manufacturing, sustainability
must also be consistent with your
business model. If it isn’t, you run the risk
of having a very sustainable operation
from an environmental perspective, but
not a business perspective because it fails
to provide the required cash flow. Such
was the case for a manufacturer of net to
near-net shaped formed and extruded
components, which drove them to
entertain the thought of improving their
waste treatment process.
The process had already advanced
from the classic calcium chloride
and anionic coagulant to a more
sophisticated polymer coagulation-
neutralize-clarification process with
a modest chemical spend of $300,000
The primary sources of waste fluid are a phosphate line and
some process cleaning baths. A review of the sources revealed
that there was potential to introduce an additional polymer in
the coagulation process. At what cost, you might ask, and for
what purpose? The cost of the polymer was estimated at $5,000
annually. However, this additional cost would reduce the
coagulant usage by over $100,000!
As technology continues to advance, so do opportunities
for improvement. The “we have always done it this way”
mentality certainly has great ability to sustain a business, and
the tendency to not fix something that is not broken can carry
a lot of weight. Still, as opportunities for improvement present
themselves, revisiting an old process can lead to significant
A typical waste reduction system setup.
Adding Manufacturing Capabilities
It is obvious that a change to your manufacturing process
will change your waste stream and waste treatment. Perhaps
you are considering upgrading your capabilities to include
e-coat and powder coating applications. Let’s take a look at a
retail equipment manufacturer who upgraded their capabilities
from electroplating only, adding e-coat and powder coating.
Making this upgrade results in a situation where acidic and
anionic wastewater comingle with the chrome wastewater,
interfering with the reduction of chrome and the precipitation
of the chrome, nickel and zinc. When the waste stream
changes from electroplating to powder and e-coat, the
increased anionic waste requires slug dosing of calcium
chloride. While the waste is still predominantly the result
of electroplating, the variability can go from one extreme to
another depending on manufacturing needs.
|Normal flow ratio [of total]:
|Variance in Flow:
Supplemental calcium chloride dosing provided some
assistance; however, the periodic waste source changes made
the calcium demand erratic and essentially impossible to
control on a consistent basis. The soluble and suspended solids
excursion events caused the sand filter to plug routinely with
zinc, nickel, and chrome hydroxide-based suspended solids.
It is clear to see that the new variability of the waste needed
a more tailored and robust solution. Testing revealed that the
surfactants in the powder/e-coat were the primary cause of
the suspension. By designing the waste treatment chemistry to
address the swings to 100 percent of either the electroplating
waste or the powder/e-coat waste, at a modest treatment rate
of 200 ppm the metal hydroxides were adequately formed and
coagulated. After pH adjustment, a dose of 2.5 ppm polymer
was successful at flocculating the waste.
A consistent solids conditioning and neutralization of
all wastewater sources, in both net anionic and cationic
charge differentials, was obtained. A sludge reduction of
approximately 15 percent was achieved by the application of
the mixed chloride coagulant at a dosage of 200 ppm versus
the previous periodic slug dosing of calcium chloride. The
sand filter continuous backwash procedure maintained a
clean media surface and the sand filter media did not foul
with carbonate salts. Ongoing regulatory compliance for zinc,
nickel, and chrome was realized with no reported excursions.
The Upgrades You Need
The waste stream is often overlooked in the effort
to quickly produce parts. We all need a strong focus on
delivering what the customer wants in order to stay relevant
and marketable. From proper equipment utilization to
updated chemistries, partnering with a knowledgeable and
reputable supplier for an evaluation of waste treatment
processes can put your mind at ease about reducing waste,
leaving you free to focus on the manufacturing process.
Mark Fretz is product manager – metalworking and water
treatment at Chemetall, a BASF company.