vvEPA
United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S-92/012 May 1992
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a Manufacturer of
Commercial Ice Machines and Ice Storage Bins
F. William Kirsch and Gwen P. Looby*
Abstract
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 Man ual (EPA/625/7-88/003, July
1988). The WMAC team at Colorado State University per-
formed an assessment at a plant that manufactures commer-
cial ice machines and ice storage bins. The surface treatment
of fabricated steel parts, parts washing, and treatment of waste-
water generate the majority of this plant's waste. The team's
report, detailing findings and recommendations, indicated that
the greatest waste reduction would result from reusing rinse
water in the plant's five-stage washer for fabricated parts.
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, which is available from the authors.
Introduction
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 19104.
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 Colorado
State University's (Fort Collins) 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-
tion.
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 proce-
dures outlined in the EPA Waste Minimization Opportunity
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
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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
This plant manufactures commercial ice machines and ice
storage bins. Typically, 270 employees produce 26,000 ice
machines and 12,500 ice bins annually. Areas of the plant
operate between 2,210 and 7,488 hr/yr.
Manufacturing Process
The framework and outer body parts of the products are
fabricated from galvanized and rolled steel sheets. The sheet
metal is cut to size, punched, and drilled by brake presses and
numerically controlled punches.
Those steel parts are then sent through a five-stage washer to
prepare their surfaces for coating. The washer consists of an
enclosed spray booth through which a conveyor passes. The
first stage degreases the steel parts with an aqueous spray of
potassium hydroxide cleaner. Overspray and excess fluid drain
back into a 2,000-gal collection tank for reuse. Waste is gener-
ated only when the tank is dumped about once each month. All
of the wastewaters from the washer drain to the on-s'rte waste-
water treatment unit and are eventually sewered and fed to the
POTW.
The second stage of the washer is a continuous rinse that
sprays the metal parts with tap water to remove the cleaner
and remaining contaminants. A tank below the spray nozzles
collects rinse water that drains from the parts. This stage is
designed so that clean tap water is sprayed onto the parts last.
A pump supplies high-pressure water from the collection tank
to provide initial rinsing. In addition to a continuous overflow of
about 8 gpm of rinse water, the 1,200-gal collection tank is
dumped on a daily basis.
The third stage sprays an aqueous solution of iron phosphate/
phosphoric acid (typical pH of 5.5) on the parts. The phosphating
solution reacts with the metal surface to provide an amorphous
coating of iron oxides and phosphate that serves as a base for
the powder coating. The phosphating stage only generates
waste when the collection tank is dumped, typically on a
monthly basis.
The fourth stage is another tap-water rinse to remove excess
phosphating solution. In addition to a continuous rinse water
overflow of about 9.5 gpm, the 650-gal collection tank is dumped
on a daily basis.
The fifth stage of the washer is a closed-loop, chromated-water
spray rinse, which provides a mild conversion coating to the
parts. Metal parts are sprayed with about 33 gpm of an aque-
ous solution to which chromic trioxide has been added. The
collection tank is connected to a treatment unit that contains
three ion-exchange cartridges. Treatment of the chromated
water is performed on a batch basis, typically every three
weeks; treated liquid drains to the wastewater treatment unit.
The spent resin cartridges are drummed and returned to the
supplier for recycling. Following this rinse, the parts are air
dried.
Next the steel parts are painted with powder coating and baked
in a 400°F natural gas-fired oven to bond the powder coating to
the parts' surfaces. These finished cabinet components are
then sent to the final assembly area.
This plant manufactures onsite the flaker barrel/evaporator as-
sembly and the down chute for directing the flow of ice flakes
for the flaked ice machines produced. Brass tubes for the f laker
barrels are milled, drilled, and threaded. Copper tubing is then
wrapped around the barrel and the assembly is cooled with
water. A heated brass shell is shrink-fitted onto the cooled
assembly and brazed onto the barrel.
The flaker barrel/evaporator assemblies are then sent through
a bright dip process that provides corrosion protection to the
assemblies. Brass barrels and brass/copper evaporator assem-
blies are first dipped in an aqueous brightening solution con-
taining nitric acid and calcium nitrate for about 75 seconds. The
solution loses its effectiveness after cleaning about 100 evapo-
rators and is drained and regenerated about twice per week.
The spent solution, which contains copper sulfate and copper
nitrate crystals, is drummed and returned to the supplier to
recover the copper.
A dead rinse bath and heated rinse bath of tap water follow
cleaning. After rinsing, the barrel assemblies are placed on drip
boards to allow liquids to drain back into the rinse baths. These
rinses are drained daily to the wastewater treatment unit. Rinses
typically contain copper and lead in solution, along with re-
agents carried into the rinse baths as drag-in.
A chemical sealant is then applied to the assemblies to allow
for service in food-related areas. The barrels are plunged
quickly into a succession of baths containing an aqueous solu-
tion of soda ash, tap water, and an aqueous sealant containing
isopropyl alcohol and potassium hydroxide. These baths are
drained and regenerated about once per week. The spent
solutions flow to the wastewater unit for neutralization and
disposal.
Following the chemical cleaning and sealing, the finished bar-
rel/evaporator assemblies are placed into a mold. Self-skinning
polyurethane foam insulation is blown into the mold and onto
the outer surface of the assemblies.
Down chutes are fabricated from sheet metal and then insu-
lated with blown polyurethane foam.
The evaporators for the ice machines that make cubed ice are
also manufactured in-house. The evaporator assembly consists
of a grid of criss-crossed copper strips that form the framework
inside a copper pan.
All copper parts are first chemically cleaned in a degreasing
solution and an aqueous solution of 5% hydrochloric acid. The
tanks are drained and replenished twice a week. Spent solu-
tions flow to the wastewater treatment unit for neutralization
and disposal.
Slots are then cut in the copper strips using punches. The pans
are formed from copper sheets. The grid, which is made up of
copper strips, is then assembled in the pan.
Copper tubing is bent into a serpentine shape and bonded to
the reverse side of the copper pans with solder in an electric
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soldering oven. The evaporator assemblies are then cleaned in
an enclosed washer to remove excess solder flux that clings to
the copper surfaces. The cleaning solution contains a mild acid
to remove corrosion and metallic oxides. Overflow from the
washer drains to the wastewater treatment unit. The cuber
evaporator assemblies are then sent offsite for tin plating.
In the final assembly area, completed evaporator assemblies
and painted panels are assembled with motors, pumps, con-
densers, controls, and other parts to form flaked- and cubed-
ice machines. Tubing is brazed together and tested for leaks in
separate pressure tests with air and Freon 22. Further vacuum
tests are performed on the completed refrigeration system. The
units are then charged with either Freon 502 or Freon 12. Each
ice maker is tested to assure quality ice production. Final
insulation and outside panels are installed on the ice makers
before they are packed and stored in the finished-goods ware-
house to await shipping.
Ice bins are constructed of sheet metal panels with a plastic
inner liner. Polyurethane foam is placed between the sheet
metal and the plastic by a high-pressure foaming system. Final
assembly includes cleaning and installing doors. Completed
bins are packed and stored in the finished-goods warehouse to
await shipping.
Wastewater from various operations in the plant drains to a
holding tank. When the tank becomes full, the water is pumped
to an acidification tank, where sulfuric acid is added to lower
the pH to between 3.5 and 1.9. An aqueous solution of slaked
lime is added in an initial neutralization tank to precipitate
metal hydroxides and raise the pH to between 3.5 and 6.5. The
pH is raised to between 6.0 and 9.5 in a second neutralization
tank to allow for discharge to the POTW. After neutralization, a
polymeric flocculent is added; the resulting sludge and super-
natant are then forced through a filter press. From analytical
tests performed by company personnel and outside labs, the
dried sludge is known to contain copper and lead hydroxides in
small amounts and is classified as non-hazardous waste. The
sludge is therefore hauled to a non-hazardous waste disposal
facility, where it is incorporated in the formulation of concrete.
The supernatant liquid is discharged to the POTW as industrial
wastewater.
Other sources of waste from this process include the following:
• Petroleum naphtha is used to clean tools and dies. Spent
solvent is exchanged for fresh solvent and recycled by the
supplier.
• Methylene chloride is used to clean the nozzle that mixes
isocyanate and resin to form the polyurethane foam insu-
lation for flaker barrel assemblies and down chutes. The
nozzle must be cleaned out quickly after each use be-
cause the foam will set in about 20 seconds. A combined
solution of waste polyurethane and spent methylene chlo-
ride is drummed and shipped to a hazardous waste facil-
ity. ' '
• Waste oil is generated from annual drainage of hydraulic
fluid reservoirs in metal-forming machines. Vacuum pumps
from the testing area are occasionally drained and replen-
ished. These streams are combined and sent to a non-
hazardous waste oil recycling firm that filters and dewaters
the oil for use as industrial boiler fuel.
Existing Waste Management Practices
The following waste minimization techniques have been imple-
mented at this facility:
• A formal, written waste minimization policy has been de-
fined by management, complete with cause champions.
• Powder coatings have been used since 1985 to replace
solvent-based paints for metal parts.
• Organic cleaning wastes have been reduced in the bin-
foaming area by the installation of the high-pressure foam-
ing system.
• Excess metal is segregated onsite and sold to a scrap-
metal dealer for recycling.
• A preventive-maintenance program has been developed
for the machinery used in metal-forming operations.
« Waste oils, spent bright dip solutions, spent solvent, and
ion-exchange cartridges from the final stage in the sur-
face-treatment process are recycled.
• The final rinse in the washer prior to powder coating is a
closed-loop rinse that involves separate treatment with an
ion-exchange unit.
• Rinse water flow rates in the washer prior to powder
coating have been reduced to the lowest possible levels
deemed feasible by company personnel.
• Counterflow rinsing is used within the rinse stages of the
washer prior to powder coating. Within each rinse stage,
the initial rinse uses water from the drainage-collection
' tank, and the final rinse is fresh tap water.
• A dead-rinse tank is used in the bright dip process to
collect drag-out before workpieces are dipped in heated
rinse water.
• Drain boards are used following rinses in the bright dip
process.
• Wastewater treatment sludge is partially dewatered by a
filter press.
• Methylene chloride replaced methyl ethyl ketone (MEK) in
1984 to clean foamer nozzles for the flaker assemblies.
• Drip bars are used for the degreasing bath and acid bath
of the small parts washer.
Waste Minimization Opportunities
Table 1 summarizes the principal sources of waste, their
amounts, the management method applied and the associated
costs.
Table 2 gives a brief description of the waste minimization
opportunities recommended for this plant, the current plant
practice, together with savings and cost data.
It should be noted that, in most cases, the economic savings of
the minimization opportunities result from the need for less raw
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material and from reduced present and future costs associated
with hazardous waste treatment and disposal. Other savings
not quantifiable 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.
Table 1. Summary of Current Waste Generation
Annual Quantity
Generated
Waste Stream
Waste Generated
Management Method
Annual Waste
Management
Costs($)
Liquid Wasta
A Surface Treatment:
Cleaner (Stags 1)
Rinsa (Stage 2)
Iron Phosphate (Stage 3)
Rinse (Stage 4)
Chromated Rinse (Stage 5)
B. Bright Dip:
Brightener
Soda Ash
Seatar
Rinses
C, Copper Parts Washer:
Degraaser
5%HCI
Tap water laden with dirt, oil, and
potassium hydroxide cleaner
Tap water laden with dirt, oil, and
potassium hydroxide cleaner
Tape water laden with iron phosphate
Tap water laden with iron phosphate
Closed-loop rinse water laden with
hexavalent chromium
Spent brightener containing copper
nitrate and copper sulfate crystals
Spent sodium hydroxide
Spent sealer containing isopropyl alcohol
and potassium hydroxide
Tap water laden with brightener, sealer,
soda ash, and copper in solution
Tap water containing alkaline degreaser,
grease, and oil
Tap water containing hydrochloric acid
24,000
2,545,900
14,400
2,781,500,
16,900
660
1,000
1,000
10,300
10,400
10,400
Pretreated and sewered 40
Pretreated and sewered 4,280
Pretreated and sewered 30
Pretreated and sewered 4,680
Recycled within closed loop; 30
periodically treated through ion-
exchange and sewered.
Filters returned to supplier
for reclamation
Returned to supplier for 1,620
copper reclamation
Pretreated and sewered 0
Pretreated and sewered , 0
Pretreated and sewered 20
Pretreated and sewered 20
Pretreated and sewered 20
(continued)
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Table 1. Continued
Annual Quantity
Generated
Waste Stream
Waste Generated
Management Method
Annual Waste
Management
Costs($)
Liquid Waste (continued)
D. Other:
Machine washer
Solvent washer
Nozzle cleaning
Waste oil
Freon
Tap water containing acid salts
Spent petroleum naphtha
Methylene chloride and polyurethane
Used hydraulic and vacuum pump oil
Discharged Freon
3,120,000
250
170
750
N/A
Pretreated and sewered 5,240
Returned to supplier for 420
reclamation
Disposal at hazardous 1,770
waste facility
Reclaimed offsite as 40
boiler fuel
Exhausted from plant N/A
Solid Waste
A. Wastewater Treatment:
Sludge
Non-hazardous metal hydroxide sludge
with grease and oils
18,200
Disposal at sanitary landfill 6,300
Table 2. Summary of Recommended Waste Minimization Opportunities
Present Practice Proposed Action
Waste Reduction and Associated Savings
The rinse from stages two and four of
the five-stage washer are dumped to
the sewer on a daily basis.
Flaker barrel evaporator assemblies
are cleaned in the bright dip line.
Redirect the rinse water overflow from the fourth
stage for reuse in the second stage rinse thereby
eliminating the fresh water make-up in the second
stage. Waste reduction and cost savings will result
from eliminating the disposal of spent brightener
and rinses. Cost savings wall result from the reduced
amount of water that must be purchased, treated,
sewered.
c.
Install a plastic media blasting unit to replace the
existing chemical cleaning line. The proposed
system would use air pressure to propel plastic
granules that provide mildly abrasive cleaning.
Waste reduction will result from eliminating the
disposal of spent brightener and rinses. Cost savings
will result from the avoided purchase of brightener and
reduced disposal costs. It should be noted that the
caustic bath, a rinse, and the sealant will still be
required.
Waste reduction = 2,171,520 gal/yr
Cost reduction = $4,630/yr
Implementation cost = $800 ,
Simple payback = 0.2 yr
Waste reduction = 9,960 gal
Cost reduction = $3,950/yr
Implementation cost = $5,000
Simple payback = 1.3 yr
•&V.S. GOVERNMENT PRINTING OFFICE: 1992 - 648-080/40257
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BULK RATE
United States Center for Environmental POSTAGE & FEES PAID
Environmental Protection Research Information EPA
Agency Cincinnati, OH 45268 PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/600/S-92/012
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