United States
                         Environmental Protection
                                                               Risk Reduction
                                                               Engineering Laboratory
                                                               Cincinnati OH 45268
                         Research and Development
                                                                EPA600/S-92/018 April 1992
                       RESEARCH   BRIEF

Waste Minimization Assessment for an Aluminum Extrusions Manufacturer
                               Gwen P. Looby and F. William Kirsch*
The U.S. Environmental Protection Agency (EPA) has funded
a pilot project to assist small- and medium-size manufacturers
who want to minimize their generation of waste but who lack
the expertise to do so. Waste Minimization Assessment Cen-
ters (WMACs) were established at selected universities and
procedures were adapted from the EPA Waste Minimization
Opportunity Assessment Manual (EPA/625/7-88/003, July 1988).
The WMAC team at the University of Tennessee performed an
assessment at a plant manufacturing aluminum extrusions 
over 36 million Ib/yr.  Primary and scrap aluminum is melted
down, cast into logs, then heat treated.  Next,  the  logs are
extruded into desired shapes.  Extrusions are sheared, heat
treated, then either buffed, anodized (colorized), painted, or
shipped. The team's report, detailing findings and recommen-
dations, indicated that the majority of waste was generated in
the anodizing line but that the greatest savings could be ob-
tained by installing an electrostatic powder coating system to
eliminate spent toluene,  air filters,  plastic sheets, paint ash,
and evaporated solvents.

This Research Brief was  developed by the principal investiga-
tors and EPA's Risk Reduction Engineering Laboratory/Cincin-
nati, OH, to announce key findings of an ongoing  research
project that  is fully documented in a separate report of the
same title available from the authors.
The amount of waste generated by industrial plants has be-
come an increasingly costly problem for manufacturers and an
additional stress  on the environment.  One solution to the
1 University City Science Center, Philadelphia, PA 19104
                                                 problem of waste is to reduce or eliminate the waste at its

                                                 University City Science Center (Philadelphia, PA) has begun a
                                                 pilot project to  assist small- and  medium-size manufacturers
                                                 who want to minimize their formation of waste but who lack the
                                                 inhouse expertise to do so. Under agreement with EPA's Risk
                                                 Reduction  Engineering Laboratory, the Science  Center has
                                                 established three WMACs.  This assessment was done by
                                                 engineering faculty and students at the  University of
                                                 Tennessee's (Knoxville) WMAC.  The assessment teams have
                                                 considerable direct experience with process operations in manu-
                                                 facturing plants and also have the  knowledge and skills needed
                                                 to minimize waste generation.

                                                 The waste minimization assessments are done for small- and
                                                 medium-size manufacturers at no out-of-pocket  cost to the
                                                 client.  To qualify for the assessment, each client must fall
                                                 within Standard Industrial Classification Code 20-39, have gross
                                                 annual  sales not exceeding $50 million, employ no more than
                                                 500 persons, and lack inhouse expertise in waste minimization.

                                                 The potential benefits of the pilot project include minimization
                                                 of the amount of waste generated by manufacturers, reduced
                                                 waste treatment and disposal costs for participating  plants,
                                                 valuable experience for graduate  and undergraduate students
                                                 who participate in  the program,  and a cleaner environment
                                                 without more regulations and higher costs for manufacturers.

                                                 Methodology of Assessments
                                                 The waste minimization assessments require several site visits
                                                 to each client  served.   In general, the WMACs follow the
                                                 procedures outlined in the EPA Waste Minimization Opportu-
                                                 nity Assessment Manual (EPA/625/7-88/003, July 1988).  The

                                                                          (Xv Printed on Recycled Paper

 WMAC staff locates  the  sources of waste in the plant and
 identifies the current disposal or treatment methods and their
 associated costs.  They then identify and analyze a variety of
 ways to reduce or eliminate the waste.  Specific measures to
 achieve that goal are recommended and the essential support-
 ing technological and economic information is developed.  Fi-
 nally, a confidential report that details  the WMAC's findings
 and recommendations (including cost savings, implementation
 costs, and payback times) is prepared for each client.

 Plant  Background
 The plant produces  aluminum extrusions for  use by  other
 product manufacturers.   The  plant operates  6,240 hr/yr  to
 produce over 36 million Ib of aluminum extrusions.

 Manufacturing Process
 This plant forms aluminum extrusions from virgin and scrap
 metal. Raw materials for this process include primary or virgin
 aluminum ingots, scrap aluminum, and alloying metals such as
 copper, zinc, and nickel. An abbreviated process flow diagram
 is illustrated in  Rgure 1.
         Aluminum metal melted,
           cast, and extruded
                                          Dried Paint Waste
Figure 1. Abbreviated process flow diagram.
The following steps are involved in making the extrusions:

Rrst, the primary and scrap aluminum and alloying metals are
melted in natural gas-fired furnaces. Then the molten metal is
cast Into "logs" In the plant's water-quench  hydraulic  casting
system.   The logs  are  heat-treated  and extruded into the
desired cross-sectional shapes. Next the extrusions are sheared
and heat-treated again.  The finished extrusions are then sent
to the buffing, anodizing, or painting areas of the plant  for
further processing.

In the buffing area, a total of  1.3 million Ib/yr of aluminum
extrusions are manually positioned on a table where they are
passed  under a  motor-driven cloth-pad buffing wheel  several
times.  A buffing compound is sprayed onto  the pads  prior to
buffing.  Approximately 2% of the buffing compound powder is
blown onto the floor, swept up, and disposed of in municipal
waste.  Spent buffing compound is blown and aluminum dust
and buffing pad fibers are vacuum aspirated into a large water-
filled  separating tank.  Sludge is chain-raked from the bottom
of the tank and shipped to the onsite landfill. Waste water from
the separating tank is directed to  a skimming pit before being
discharged to a nearby river.  No other treatment is performed.
Used buffing pads are also disposed of in the onsite landfill.
The polished extrusions are then sent to shipping.
Anodizing                           !
Aluminum  extrusions which  require ancjdizing for  corrosion
control and coloring (14 million Ib/yr) are fjiung on an overhead
crane to facilitate dipping into a series of fanks. The first tank
contains an alkaline detergent wash heated to 140F. A small
quantity of waste is dumped from this tank to a caustic waste
lagoon  which is  part  of the  plant's  waste water  treatment
system.  The parts are then dipped in a Irinse tank  (tank #2);
overflow from this tank is directed to thej rinse tank (tank #4)
that follows the etch tanks described beloW.
Approximately 98% of those parts are then processed in one of
two steam-heated etch tanks which contain sodium hydroxide
and caustic solution. In the etch tanks, small quantities of the
product surfaces are chemically removed in preparation for
further treatment. Waste water from the e^ch tanks is sent to a
reaction pit which is part of the waste water treatment system.
Gases emitted  from the two  etch tanks are directed through
duct work to a water spray fume scrubber. Waste water from
the fume scrubber is sent to the caustic waste lagoon.

After etching, the extrusions are rinsed in  two tanks (tank #4
and tank #6). The first rinse tank (tank #4) is fed by overflow
water from tank #2 that follows the detergent wash tank and
recirculated water from tank  #6.  Waste! water is fed to  the
caustic waste lagoon.                  i

The extrusions  are then sent to an acid de-smut tank which
contains hydrogen peroxide and sulfuric acid.  Waste water
from this tank is dumped once a year to an acid waste lagoon
which is part of  the plant's  waste wate|r treatment system.
Parts are then dipped in a rinse tank from which overflow water
is fed to the acid waste lagoon.          |
From that rinse tank, the extrusions are Iconveyed to one of
three anodizing tanks.  Anodizing  is an Electrolytic oxidation
process in which an aluminum oxide layer is  formed on  the
etched surface of the extrusions. This aluminum oxide layer is
extremely porous  and is useful in the coloring  of the extrusions.
Sulfuric acid  is added to each anodizing tank; fumes from
these tanks are ducted to a water spray fume scrubber which
removes carryover sulfuric acid. Scrubber! water is pumped to
the acid waste  lagoon of the water  treatment facility.  After
anodizing, the parts are spray-rinsed in one of two spray-rinse
tanks and then  water-rinsed in an ambient  tank. Waste water
from these rinses is gravity-fed to  the |acid  waste lagoon.
Extrusions  are  then  put  into a holding  tank where water is
added with a constant overflow to the acid waste lagoon.

From the holding  tank,  extrusions may be conveyed to one of
two coloring tanks or to rinse tank #19.  Approximately 30% of
the product being conveyed through the anodizing  line is  im-
mersed in a coloring tank containing sulfurp acid and stannous
sulfate.   In this tank, tin is absorbed  into the pores of  the
aluminum  oxide coating  and a  dark brown-to-black product
color results according to  customer specifications.  Color tests

are made at this point and the product may be immersed in this
solution several  times to reach the desired color.   Waste
solution from this tank is dumped once a month to the acid
waste lagoon. Next, the product is spray-rinsed and sequen-
tially dipped into two water rinse tanks (tank #19 and tank #20).
The first dip  rinse receives  overflow water from the second
rinse tank.  Waste water from all three  of the aforementioned
rinse steps is pumped to the acid waste lagoon.  From rinsing,
the extrusions are conveyed to one of three color sealant tanks
which contain a  nickel fluoride sealant.  The product is then
passed through a final rinse stage before air-drying and ship-

The second coloring tank contains a Sandoz bronze solution
which also is absorbed into  the pores of the product surface
but results in a bronze-colored product. Only  about  1% of
product goes through this coloring process.  Waste water from
the Sandoz bronze tank  is dumped once  a year to the acid
waste  lagoon.  From this coloring tank, parts are  rinsed in  a
water tank and then immersed in a nickel sealant tank.  Parts
are then water-rinsed and  air-dried before shipping.  Waste
water from these rinse and sealant tanks is pumped to the acid
waste lagoon.

The remaining 69% of the  product that is sent through the
anodizing  line is sent directly to  rinse tank  #19,   which
precedes  the nickel fluoride sealant tanks  mentioned in the
sulfuric acid-stannous sulfate coloring process. After rinsing in
tanks 19 and 20, these  extrusions are sealed in the  nickel
fluoride sealant tanks, rinsed, air-dried, and sent to shipping.

Approximately 21  million Ib/yr of the extrusions are painted
before shipping.   Extrusions to be painted are manually hung
on an overhead conveyor system which transports them through
a  series of spray booths for pretreatment  and painting.  The
first pretreat  booth  consists of  a recirculated heated alkaline
cleaner spray which removes  dirt and  grease.  Waste water
from this  step is dumped to the chromium  treatment tanks
which  are  part  of the plant's waste  water treatment system.
Next, parts are  spray-rinsed and conveyed through a spray
chromic acid surface treatment booth  which enhances  paint
adhesion.  Drag-out and  evaporative losses  are so excessive
that the  chromic surface treatment  collection tank is never
dumped.   Waste hexavalent chromic acid  is pumped to the
chromium  treatment tanks.   The chromic  acid treatment of
extrusions  is followed by two rinse stages which complete the
pretreatment steps in the paint line.  Waste  water from those
rinse tanks is also pumped to the chromic treatment tanks.

Next, extrusions are conveyed through a natural gas-fired dry-
off oven (250F) before passing through two electrostatic,paint
booths.  Over 180 different  colors of paint are used, most of
which  are polyester and acrylic with the remaining paint being'
fluorocarbon-based.  To  achieve the desired color,  the plant
has six paint mixing stations. Acrylic and polyester paints are
thinned with a  "150 solvent".   Fluorocarbon paint is thinned
with  both  methyl  isobutyl  ketone  (MIBK) and "DB" solvents.
Toluene is pumped through the  lines for cleaning  between
color changes.  Air filters  in the paint booths  are  changed
periodically; plastic sheeting is placed  on the floor to collect
paint overspray.  The plastic  and filters are removed to a
landfill.  Paint-contaminated toluene is collected in barrels and
hauled offsite as a hazardous waste.  Toluene also evaporates
to the plant atmosphere.   After painting, the extrusions  are
conveyed through a gas-fired bake oven (350-480F) for 10 to
12 min, manually removed from supporting  conveyor hooks,
and  transferred to shipping. Unsatisfactorily painted  stock is
transported to the melt oven and used as scrap charge. Paint-
laden conveyor hooks  are periodically put in a natural gas-fired
burn-off oven for paint removal by incineration; ash is hauled
away with air filters and plastic sheeting as a non-hazardous

Existing Waste Management Practices
    Toxic hexavalent  chrome is transformed to non-toxic
     chrome before offsite shipment.
    An onsite waste water treatment facility controls sus-
     pended and dissolved species concentrations in efflu-
     ent water.
    A water-spray fume scrubber  is utilized in the anodiz-
     ing area for air quality control.

Waste Minimization Opportunities
The  type of waste currently generated by the plant, the source
of the waste, the  quantity of the waste, and the annual man-
agement costs are given in Table  1.

Table 2 shows the opportunities for waste minimization that the
WMAC team recommended for the plant. The type of waste,
the minimization opportunity, the possible waste reduction and
associated savings, and the implementation cost along with the
payback time are given  in the table.  The quantities of waste
currently generated by the plant and  possible waste reduction
depend on the production level of the plant.   All values should
be considered in that context.

It should be noted that, in most cases, the economic savings of
the minimization opportunities result from the need for less  raw
material and from reduced present and future costs associated
with waste treatment and disposal. Other savings not quantifi-
able  by this study include a wide variety of possible future
costs related to changing  emissions standards,  liability, and
employee health.  It  should also be noted  that the savings
given for each opportunity reflect the  savings achievable when
implementing  each waste  minimization opportunity  indepen-
dently and  do not  reflect  duplication  of savings that would
result when the opportunities are implemented in a package.

This research brief summarizes a part of the work done under
Cooperative Agreement No. CR-814903 by the University City
Science Center under the sponsorship of the U.S. Environmen-
tal Protection Agency.  The EPA Project Officer was Emma
Lou  George.

Ttbla 1. Summary of Currant Waste Generation
Wests Generated
Butting compound sludge
Used buffing pads
Spent toluene
Evaporated toluene
Used air fitters, used plastic
shoaling, and paint ash
Evaporated paint solvents
Trivalant chromic sludge
Waste water sludge
Waste water
Source of Waste

Water-filled separating tank in the buffing line.
Sludge is disposed in the on-site landfill.
Cloth-pad buffing wheels in the buffing line.
Used pads are disposed in the on-site landfill.
Cleaning of paint lines between color changes.
Spent toluene is hauled off-site as a hazardous waste.
Cleaning of paint lines.

Electrostatic paint booths. Used air filters,
used plastic sheeting, and ash which results
from the removal of paint from conveyor hooks
in the burn-off oven are combined and hauled
away as non-hazardous waste.
Bake oven in the paint line.

Clarifior following the chromium treatment tanks
in the waste water treatment system.
Chromic sludge is disposed in the on-site landfill.
Clariffer fed by the acid and caustic waste lagoons and
the reaction pit in the waste water treatment system.
Sludge is disposed in the on-site landfill.
Waste water treatment system.
is discharged to a nearby river.
After treatment, water
Quantity Generated A
26,000 Ib
7,271 pads
1,430 gal
13,130 gal
50,000 Ib
6,973 gal
240,000 Ib
1, 800,000 Ib
47,160,000 gal

anagement Cost
$ 4,770

'Currently the plant reports no waste management cost associated with solvent evaporation.
*Currentty the plant reports no waste management cost associated with water discharge.

Table 2.  Summary of Recommended Waste Minimization Opportunities

Waste Generated                      Minimization Opportunity
Annual Waste Reduction     Net    Implementation Payback
   Quantity  Per Cent  Annual Savings   Cost       Years
Spent toluene
Evaporated toluene
Used air filters, used plastic sheets,
and paint ash
Evaporated paint solvents
Waste water sludge
Buffing compound sludge
 Spent toluene
 Waste water sludge
 Waste water
   6,973 gal    100
Replace the solvent-based painting         1,430 gal    100
system with an electrostatic powder         13,130 gal    100
painting system.  The proposed system     50,000 Ib    100
will eliminate the need for paint solvents
and spray gun and paint line cleaning.
In addition, the powder coating will
provide for more even coating of the
product surfaces and easy collection
and reuse of overspray powder.

Reduce drag-out from the tanks in the        3,600 Ib       0.2
anodizing line. An array of rinse spray
nozzles should be installed above  the
detergent, etch, acid de-smut, anodizing,
stannous sulfate, nickel fluoride seal,
"Sandoz" bronze, and "Sandoz" seal tanks
to spray water onto each parts rack as it
is raised from the tank. Drag-out boards
should be installed on all tanks in  the line
and the drain time of parts over the tanks
should be increased.

Install an automatic metering system         5,200 Ib      20
to minimize the amount of buffing
compound used.

Recover spent toluene using a distillation    1,144 gal     80
unit.  The recovered toluene can be used
for cleaning the paint lines.

Recover and recycle caustic and acid        3,600 Ib       0.2
solutions in the rinse tanks of the         40,000,000 gal   85
anodizing process line. Install dedicated
reverse osmosis (RO) solution recovery
systems on the rinse tanks following the
etch,  acid  de-smut, and "Sandoz" bronze
tanks. An  electrodialysis unit in series with
the etch rinse tank RO system Will be required
to remove  aluminum hydroxide before reuse.
Waste water collection tanks with  RO units
should be installed beneath the spray rinses
that precede the anodizing and stannous
sulfate tanks. In addition,  the flow rates of
water through the rinse tanks should be
lowered to 5 gpm; air agitation units should
be installed in the tanks to increase rinsing
effectiveness and to  compensate for the
lower flow rates.  Savings will result from
recovery of raw materials lost in the rinsing
operations and reduced water purchases.
                                                                                                 $1,084,440'    $147,580     0.1
                                        28,910     0.5
                             6,590*       25,960   3,9
                                                                                                      17,030s       37,060     2.2
                           105,480s      419,160     4.0
 'Includes raw material cost savings attributed to the lower cost of powder coatings.
 includes raw material cost savings.
                                                                                             U.S. Government Printing Office: 1992  648-080/60076



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