United States
                         Environmental Protection
                                         Risk Reduction
                                         Engineering Laboratory
                                         Cincinnati OH 45268
                         Research and Development
                                        EPA600/S-92/006 April 1992
               Waste Minimization Assessment for a Manufacturer of
                        Metal-Cutting Wheels and Components

                               F. William Kirsch and J. Clifford Maginn"
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 hazardous waste but
who lack the expertise to do so.  Waste Minimization Assess-
ment Centers (WMACs) were established at selected universi-
ties and procedures were adapted from the EPA Waste Minimi-
zation 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 metal-
cutting wheels and components — approximately 6,000,000
units/yr. Tungsten carbide inserts for metal cutting are pressed,
sintered, shaped by grinding, and ultrasonically cleaned. About
half are coated with titanium nitride by chemical vapor deposi-
tion.  Premolded ceramic inserts are ground to specifications
and ultrasonically cleaned.  Steel disks  for diamond-plated
cutting wheels are machined, cleaned, treated  with sulfuric
acid,  coated with a diamond abrasive  compound in a nickel
lattice (plated from a nickel sulfamate  solution)  and given a
final electroless plating of nickel. Aluminum and aluminum-
resin  disks for diamond cutting wheels are machined to work-
ing specifications, a diamond abrasive compound is applied,
and the wheels  are machined to final specifications.  The
team's report,  detailing findings  and recommendations,  indi-
cated that most waste, other than treated wastewater, consists
of sludge filtered from machine coolant, and that the greatest
savings could be obtained by recycling  treated water from the
plant's wastewater treatment facility to  the gas/water separa-
tors of the chemical vapor deposition units.

This Research Brief was developed by the principal investiga-
tors and EPA's Risk Reduction Engineering Laboratory, Cincin-
* University City Science Center, Phlladefchia, PA 19104
                         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 hazardous waste generated by industrial plants
                         has become an increasingly costly problem for manufacturers
                         and an additional stress on the environment. One solution to
                         the problem of hazardous waste is to reduce or eliminate the
                         waste at its source.

                         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 hazardous waste but
                         who lack the in-house expertise to do so.  Under agreement
                         with EPA's Risk  Reduction Engineering Laboratory, the Sci-
                         ence 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
                         manufacturing plants and also have the knowledge and skills
                         needed to minimize hazardous 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 in-house expertise  in waste minimiza-

                         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,

                                                   s£> Printed on Recycled Paper

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
WMAC  staff locates the sources of hazardous  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 supporting technological and economic information is
developed. Finally, a confidential report that details the WMACs
findings and recommendations (including cost savings,  imple-
mentation  costs,  and payback times) is  prepared for each

Plant Background
The plant manufactures metal-cutting wheels and components.
The plant  operates  8,400 hr/yr to  produce approximately
6,000,000 units.

Manufacturing Process
The plant  makes  tungsten carbide metal  cutting inserts, ce-
ramic metal cutting inserts, diamond-plated cutting wheels and
diamond cutting wheels. Raw materials include tungsten car-
bide powder, premolded baked ceramic pieces, steel  disks,
aluminum-resin mixture, forged and cast aluminum disks, sol-
vents, and chemical reagents.

  • Tungsten Carbide Metal-Cutting Inserts

    Tungsten carbide  powder with binder is pressed into
    insert shapes, sintered, and shaped by grinding.  After
    ultrasonic cleaning, 50% of the parts are packaged,
    45% are coated  with titanium nitride (by chemical
    vapor  deposition) and  packaged,  and  5% are
    electropolished (chemically  etched), coated with tita-
    nium nitride and packaged. Wastes generated are
    spent  solvent (trichloroethane) used to clean press
    and die parts, spent solutions from ultrasonic clean-
    ing, spent acid hydrite (a commercial mixture of sulfu-
    ric and phosphoric acids) from electropolishing, efflu-
    ent water from chemical  vapor  deposition furnace
    exhaust scrubbing,  and spent rinse  water.   Spent
    trichloroethane and spent acid hydrite are shipped to
    an offsite recycler, and the spent cleaning solutions,
    scrubber effluent,  and rinse waters are piped to the
    plant's wastewater treatment system.  Grinding cool-
    ant is filtered and recirculated.

  « Ceramic Metal-Cutting Inserts

    Premolded inserts are ground to specifications.  After
    ultrasonic cleaning, the ceramic inserts are marked
    with ink and  packaged.  Grinding coolant is filtered
    and recirculated.

  • Diamond-Plated Cutting Wheels

    Steel  disks are machined, cleaned  with acetone,
    cleaned further in a detergent bath, given surface
    treatment in sulfuric acid, coated with a diamond abra-
    sive compound in a nickel lattice (plated from nickel
    sulfamate solution), and given a final "electroless plat-
    ing" of  nickel.   Wastes generated are  scrap  from
    machining,  spent solvent (acetone), spent cleaning
    rags, and spent detergent and reagent solutions. Spent
    acetone is  sent to  a recycler, the spent  rags are
    laundered offsite, and spent detergent and reagent
    solutions are piped  to the plant's wastewater treat-
    ment system.

  • Diamond Cutting Wheels

    Purchased aluminum disks and aluminum-resin disks
    manufactured in the  plant are used. Both forged and
    cast aluminum disks and the  aluminum-resin disks
    are machined  to working specifications.  A diamond
    abrasive compound  (including hexavalent potassium
    chromate) is then applied in a press, and the wheels
    are machined and  ground to final  specifications.
    Wastes  generated are aluminum and aluminum-resin
    scrap from  machining and grinding, and spent chro-
    mate solution.  Scrap aluminum is shipped to a scrap
    metal dealer,  waste  aluminum-resin mixture is dis-
    carded in municipal trash, hexavalent chromate solu-
    tion is converted to  the  less toxic trivalent by treat-
    ment  with sodium bisulfate and hydrated  lime and
    piped to the plant's wastewater treatment system, and
    grinding coolant is filtered and recirculated.

  • Wastewater Treatment

    Spent solutions and rinse waters are pH adjusted and
    pumped to  a floe tank before  settling in a clarifier.
    Decanted water is discharged to the municipal sewer
    system,  and sludge  is partially dewatered in  a sand
    bed filter and shipped for disposal as hazardous waste.

  • Coolant Filtering

    Spent machine  coolant is  filtered under  pressure
    through diatomaceous  earth.    The  coolant  is
    recirculated to the process, and sludge,  which  con-
    tains tungsten carbide, synthetic diamonds and diato-
    maceous earth, is shipped offsite for reclamation.

Existing Waste Management Practices
  • Spent hexavalent chromate solution is converted to a
    less toxic trivalent form by treatment with  sodium
    bisulfate and hydrated lime.

  • Process wastewater  is treated in  the plant by pH
    adjustment  and flocculation before discharge to the
    municipal sewer.

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 treat-
ment and disposal costs are given'in Table  1.

Table 2 shows  the opportunities for waste minimization and
cost savings that the WMAC  recommended to the plant.  The
minimization opportunities, the  possible waste reduction and
associated savings, and the implementation cost with payback
time are listed in the table. The quantities of waste generated
and possible waste reduction depend on the production level of
the plant.  The values shown  should  be  considered  in that

It should  be noted that the economic savings of the WMOs
address only the raw material cost avoidance and reduction of
present and future costs associated with waste treatment and
disposal.  Other savings not quantifiable by this study include
possible future costs related to changing emission standards,
liability, and employee health.  It should also be noted that the
savings given for each opportunity reflect the savings achiev-
able when implementing each waste minimization opportunity
independently and do  not  reflect  duplication of savings that
would  result when  the opportunities  are  implemented in a

Additional  Recommendations
In addition to the opportunities recommended and analyzed by
the WMAC team, two  additional measures were considered.
These measures  were not completely analyzed because  of
                                        insufficient data or minimal savings as indicated below.  They
                                        were brought to the plant's attention for future reference, how-
                                        ever, since these approaches to waste reduction may increase
                                        in attractiveness with changing plant conditions.

                                           «  Reduce the flows of cleaning solution and rinse water
                                             to the solution and rinse tanks used in the ultrasonic
                                             cleaning process.  (The WMAC team noted that the
                                             flows appeared to be high compared to the size of the
                                             tanks.) Test runs would be needed to obtain data on
                                             the feasibility of this measure.  Without that data, the
                                             measure is not formally recommended.

                                           •  The sludge obtained  from  the wastewater treatment
                                             sand bed filter has a 63% water content, and vibration
                                             during shipment to a landfill might cause "free water"
                                             to separate. Because of a ban on landfill disposal of
Table 1. Summary of Current Waste Generation
Waste Generated
Spent solvent
Spent solvent
Spent acid hydrite
Spent beeswax
Furnace exhaust gases
Source of Waste
Spent trichloroethane from cleaning press rams and dies is removed
from the plant by an outside recycler. Solvent vapors are lost from
cleaning troughs.
Spent acetone from diamond-plated wheel cleaning is decanted from
marking paint solids and shipped off site to a recycler. Vapors are lost
from a holding tank.
Spent sulfuric/phosphoric acid solution from electropolishing tungsten
carbide metal-cutting inserts is shipped offsite to a recycler.
Molten beeswax binder, drained from tungsten carbide insert sintering
furnaces, is cooled and discarded in municipal trash.
Sintering furnace exhausts are vented. Exhaust gases from chemical
Annual Quantity
605 gal
165 gal
324 gal
1,200 Ib
Annual Waste
Management Cost
Steel scrap and
aluminum scrap

Aluminum-resin mixture

Spent cleaning rags

Machining coolant sludge

Treated wastewater

Water treatment sludge

Waste oil

Masking paint residua
vapor deposition furnaces, used for titanium nitride coating of tungsten
carbide cutting inserts, contain titanium chloride and chlorine. These are
scrubbed with water and the effluent water piped to the plant's wastewater
treatment system.

Waste from machining of steel and aluminum cutting wheel disks is           10,000 Ib '
shipped to a scrap dealer at no charge to the plant.                         4,100 Ib *

Waste from machining of pressed aluminum-resin cutting wheel               4,500 Ibs
disks is discarded with municipal trash.

Acetone-soaked rags from spot cleaning of cutting wheel disks             480,000 rags
are laundered offsite and reused in the process.

The coolant, mainly from grinding operations, is filtered through               180,000 Ib
a diatomaceous earth filter.  The sludge obtained (72% tungsten
carbide) is reclaimed offsite. The filtered coolant is recirculated.

Rinse water from process operations and effluent water from              5,498,000 gal
chemical vapor deposition furnace exhaust scrubbers are
treated with caustic soda and calcium chloride forpH adjustment.
After flocculation and settling of sludge the water is discharged to
the sewer.

Sludge from wastewater flocculation is partially dewatered in a sand           20,000 Ib
bed filter and shipped offsite for disposal as hazardous waste.

Spent oil from maintenance is removed for off-site disposal as                 2,000 gal
hazardous waste.

Dried masking paint is manually stripped from completed                    (Unknown)
diamond-plated cutting wheels and discarded in municipal







1 Steel
2 Aluminum
                                                                             •U.S.Government Printing Office: 1992—648-080/60078

    free liquids, landfill operators may require costly addi-
    tion of cement kiln dust to soak up the free water. If
    recommended oven drying of the sludge were imple-
    mented, free water with the sludge would be reduced
    or eliminated.
                                      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.
T»blo 2. Summary of Recommended Waste Minimization Opportunities
Waste Generated
Minimization Opportunity
 Annual Waste Reduction
Quantity         Percent
Net Annual  Implementation   Payback
 Savings      Cost         Years
Spent scrubber water
Sludge from the plant's
wastowater treatment

Spent acidic degreaser
Spent trichohroethane
and acetone from cleaning
presses, maintenance
cleaning, and cleaning
cutting wheel disks
Use water from the plant's        5,292,000 gal
wastewater treatment system
in place of fresh water to scrub
the chemical vapor deposition
furnace exhaust gases.

Install a gas-fired drying oven         15,000 Ib
for dewatering the sludge.
Preclean the tungsten carbide               0
inserts with a hot water rinse
before they enter the acidic
degreaser tank.  The quantity of
degreaser solution needed will be
reduced by about 50%.

Install a batch distillation unit              493
to recover the solvents for reuse.
 $21,1681    $31,500
    9,906     16,200
                                12,333'      1,196
  3,542'     15,740
  Includes savings on raw materials.
United States
Environmental Protection
                         Center for Environmental
                         Research Information
                         Cincinnati, OH 45268
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