United States
                         Environmental Protection
                                     Risk Reduction
                                     Engineering Laboratory
                                     Cincinnati OH 45268
                         Research and Development
                                     EPA/600/S-92/012 May 1992
               Waste Minimization Assessment for a Manufacturer of
                   Commercial Ice  Machines and Ice Storage Bins

                                   F. William Kirsch and Gwen P. Looby*
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.

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-

                         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

                                                  iX& Printed on Recycled Paper

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

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
Next the steel parts are painted with powder coating and baked
in a 400F 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

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

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

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

   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

   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

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

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
Table 1.  Summary of Current Waste Generation
                                                                   Annual Quantity
Waste Stream
Waste Generated
                   Management Method
                         Annual Waste
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:


   Soda Ash



C, Copper Parts Washer:


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









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


Table 1.  Continued
                                                                      Annual Quantity
Waste Stream
                                Waste Generated
                                                            Management Method
                                              Annual Waste
Liquid Waste (continued)

D. Other:

   Machine washer

   Solvent washer

   Nozzle cleaning

   Waste oil

Tap water containing acid salts

Spent petroleum naphtha

Methylene chloride and polyurethane

Used hydraulic and vacuum pump oil

Discharged Freon




Pretreated and sewered        5,240

Returned to supplier for          420

Disposal at hazardous           1,770
waste facility

Reclaimed offsite as               40
boiler fuel

Exhausted from plant             N/A
Solid Waste

A.  Wastewater Treatment:

Non-hazardous metal hydroxide sludge
with grease and oils
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,
           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
                      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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