W-P2MF-01-02
September 2001
Environmental Technology
Verification Report
Evaluation of USFilter
Corporation's
RETEC® Model SCP-6 Separated
Cell Purification System for
Chromic Acid Anodize Bath
Solution
Prepared by
Concurrent Technologies Corporation
Under a Cooperative Agreement with
U.S. Environmental Protection Agency
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NOTICE
This publication was developed under Cooperative Agreement No. CR826492-01-0 awarded by
the U.S. Environmental Protection Agency. The Agency reviewed this document. The Agency
made comments and suggestions on the document intended to improve the scientific analysis and
technical accuracy of the statements contained in the document. Concurrent Technologies
Corporation (CTC) accommodated EPA's comments and suggestions. However, the views
expressed in this document are those of Concurrent Technologies Corporation and EPA does not
endorse any products or commercial services mentioned in this publication. The document will
be maintained by Concurrent Technologies Corporation in accordance with the Environmental
Technology Verification Program Metal Finishing Technologies Quality Management Plan.
Document control elements include unique issue numbers, document identification, numbered
pages, document distribution records, tracking of revisions, a document MASTER filing and
retrieval system, and a document archiving system.
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W-P2MF-01-02
September 2001
Environmental Technology
Verification Report
Evaluation of USFilter
Corporation's
RETEC® Model SCP-6 Separated
Cell Purification System for
Chromic Acid Anodize Bath
Solution
Prepared by
Project Manager
Chris Start
Michigan Manufacturing Technology Center
Plymouth, Ml 48170
Program Manager
Donn Brown
Concurrent Technologies Corporation
Largo, FL 33773
EPA Center Manager
Alva Daniels
National Risk Management Research Laboratory
Cincinnati, Ohio 45628
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FOREWORD
The Environmental Technology Verification (ETV) Program has been established by the U.S.
Environmental Protection Agency (EPA) to evaluate the performance characteristics of
innovative environmental technologies for any media and to report this objective information to
the states, local governments, buyers, and users of environmental technology. EPA's Office of
Research and Development (ORD) has established a five-year pilot program to evaluate
alternative operating parameters and to determine the overall feasibility of a technology
verification program. ETV began in October 1995 and was evaluated through September 2000.
EPA is preparing a report to Congress containing results of the pilot program and
recommendations for its future operation.
EPA's ETV Program, through the National Risk Management Research Laboratory (NRMRL),
has partnered with CTC under the Environmental Technology Verification Program P2 Metal
Finishing Technologies Center (ETV-MF). The ETV-MF Center, in association with the EPA's
Metal Finishing Strategic Goals Program, was initiated to identify promising and innovative
metal finishing pollution prevention technologies through EPA-supported performance
verifications. The following report describes the verification of the performance of the USFilter
Corporation's RETEC® Model SCP-6 Separated Cell Purification System for chromic acid
anodize bath solution in the metal finishing industry.
111
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ACRONYM and ABBREVIATION LIST
°C
ACGffl
Ah
CARB
CTC
DVI
dynes/cm
EFF
EPA
ETV
ETV-MF
gal
gpm
g/L
HDPE
HP
hrs/wk
ICP-AES
IDL
IN
kWh
lb.(s)
LCS
L
MDL
min
mL
mm
MMTC
MSDS
NIOSH
NRMRL
O&M
ORD
OSHA
P2
PEL
QA
QA/QC
QMP
RPD
SCP
SP
Degrees Celsius
American Conference of Government Industrial Hygienists
Amp-hours
California Air Resources Board
Concurrent Technologies Corporation
DV Industries, Inc.
Dynes per Centimeter
Effluent
U.S. Environmental Protection Agency
Environmental Technology Verification
Environmental Technology Verification Program P2 Metal
Finishing Technologies
Gallon
Gallon per Minute
Gram per Liter
High Density Polyethylene
Horsepower
Hours per Week
Inductively Coupled Plasma - Atomic Emission Spectrometry
Instrument Detection Limit
Influent
Kilowatt-hour
Pound(s)
Laboratory Control Sample
Liters
Method Detection Limit
Minute
Milliliteits)
Millimeters
Michigan Manufacturing Technology Center
Material Safety Data Sheet
National Institute of Occupational Safety and Health
National Risk Management Research Laboratory
Operating and Maintenance
Office of Research and Development
Occupational Safety and Health Administration
Pollution Prevention
Permissible Exposure Limit
Quality Assurance
Quality Assurance/Quality Control
Quality Management Plan
Relative Percent Difference
Separated Cell Purification
Sample Point
IV
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ACRONYM and ABBREVIATION LIST (continued)
SR Sample Result
S SR Spiked Sample Result
TLV Threshold Limit Value
TSA Technical Systems Audit
VDC Voltage (DC)
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ACKNOWLEDGEMENTS
This is to acknowledge Jim Totter and Valerie Whitman of CTC for their help in preparing this
document. CTC also acknowledges the support of all those who helped plan and implement the
verification activities and prepare this report. In particular, a special thanks to Alva Daniels,
EPA ETV Center Manager, and Lauren Drees, EPA Quality Assurance Manager. CTC also
expresses sincere gratitude to USFilter, the manufacturer of the RETEC® Model SCP-6
Separated Cell Purification System, for their participation in and support of this program, and
their ongoing commitment to improve metal finishing operations. In particular, CTC thanks
Mike Chan, Vice President of USFilter. CTC also thanks DV Industries, Inc. of Lynwood,
California, for the use of their facilities and materials, and the extensive contributions of Tom
Davis and Scott Smith for the performance of this verification test.
VI
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THE ENVIRONMENTAL TECHNOLOGY VERIFICATION PROGRAM
U.S. Environmental Protection Agency
Concurrent Technologies Corporation
ETV VERIFICATION STATEMENT
TECHNOLOGY TYPE:
APPLICATION:
TECHNOLOGY NAME:
COMPANY:
POC:
ADDRESS:
E-MAIL:
ELECTRODIALYSIS
CHROMIC ACID ANODIZE BATH MAINTENANCE
RETEC® Model SCP-6 Separated Cell Purification System
USFilter Corporation
David Hill
28 Cook Street
Billerica, MA 01821
hilld(ausfilter.com
PHONE: (978)262-2313
FAX: (978) 667-1731
The United States Environmental Protection Agency (EPA) has created the Environmental Technology
Verification (ETV) Program to facilitate the deployment of innovative or improved environmental technologies
through performance verification and dissemination of information. The goal of the ETV Program is to further
environmental protection by substantially accelerating the acceptance and use of improved, cost-effective
technologies. ETV seeks to achieve this goal by providing high-quality, peer-reviewed data on technology
performance to those involved in the design, distribution, financing, permitting, purchase, and use of
environmental technologies.
ETV works in partnership with recognized standards and testing organizations, stakeholder groups consisting of
buyers, vendor organizations, and states, with the full participation of individual technology developers. The
program evaluates the performance of innovative technologies by developing test plans that are responsive to the
needs of stakeholders, conducting field or laboratory tests (as appropriate), collecting and analyzing data, and
preparing peer-reviewed reports. All evaluations are conducted in accordance with rigorous quality assurance
protocols to ensure that data of known and adequate quality are generated and that the results are defensible.
The ETV P2 Metal Finishing Technologies (ETV-MF) Program, one of 12 technology focus areas under the ETV
Program, is operated by Concurrent Technologies Corporation, in cooperation with EPA's National Risk
Management Research Laboratory. The ETV-MF Program has evaluated the performance of an electrodialysis
technology for the purification of chromic acid anodize bath solution. This verification statement provides a
summary of the test results for the USFilter RETEC® Model SCP-6 Separated Cell Purification System.
VS-P2MF-01-02
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VERIFICATION TEST DESCRIPTION
The USFilter RETEC® Model SCP-6 (RETEC® unit) was tested, under actual production conditions, on a chromic
acid anodize bath solution, at DV Industries, Inc. (DVI) in Lynwood, California. Chromic acid anodizing is
performed on various aluminum parts in one of two independent parts processing tanks: a 27-foot or a 62-foot
tank. The verification test evaluated the ability of the RETEC® unit to purify the chromic acid anodize bath
solution of process contaminants in the 27-foot chromic anodizing tank.
Testing was conducted during two distinct 5-week test periods (Baseline and Operational Modes):
• During the first test period (Baseline Mode), the RETEC® unit was turned off, and the chromic acid anodizing
bath was monitored to determine the buildup rate of process contaminants. Aluminum parts were anodized at
typical processing rates for DVI.
• During the second test period (Operational Mode), the RETEC® unit was turned on, and the chromic acid
anodizing bath was monitored to determine the rate of process contaminant removal. Again, aluminum parts
were anodized at typical processing rates for DVI.
Historical operating and maintenance labor requirements, chemical usage, and waste generation data were
collected to perform the cost analysis.
TECHNOLOGY DESCRIPTION
The RETEC® Model SCP-6 Separated Cell Purification System purifies and reconditions spent chromic acid
anodizing solution by circulating it through a specialized electrochemical cell. Anodizing solution is recirculated
between the anolyte section of the RETEC® cell and the anodizing process tank. During this process, trivalent
chromium in the anodizing solution is oxidized to hexavalent chromium, and metal cations are transported to the
catholyte solution through a porous, polymeric membrane separating the anolyte and catholyte compartments of
the cell. The treated process solution is then returned to the anodizing bath. The metal contaminants removed
from the process solution are kept in solution in the catholyte side of the cell until the solution becomes saturated
with contaminants. At DVI, the RETEC® saturated catholyte waste (100 gallons) is disposed of about four times
a year.
VERIFICATION OF PERFORMANCE
In the Baseline Mode, six weekly grab samples were collected over a five-week period from the anodizing tank
and analyzed to determine the buildup rate of process contaminants. In addition, weekly grab samples from the
rinse tanks upstream and downstream of the anodizing tank were collected and analyzed for mass balance
purposes related to the anodizing tank. Rinse tank analyses showed dragout to be insignificant.
In the Operational Mode, five weekly grab samples were collected over a six-week period from the anolyte and
catholyte sections of the RETEC® unit. All samples were analyzed for process contaminants in order to perform a
mass balance and determine the removal efficiencies of process contaminants from the anodized bath solution.
Eleven weeks after the RETEC® unit was turned on (16 weeks after test started), samples were again collected
from the RETEC® unit. These samples are designated as "1Q" in Table J and represent the chemical
characteristics of the anolyte and catholyte at the end of the first quarter of the catholyte operating cycle, 11 weeks
after the RETEC® system was turned on.
Average analytical results for key parameters are shown in Table i. Hexavalent chromium is the primary active
ion in the chromic anodizing process. Trivalent chromium is the natural occurring reduced state of hexavalent
chromium. The reduction from hexavalent chromium to trivalent chromium occurs in the anodizing bath over a
period of time, and can be accelerated by temperature and pH changes, and chemical and electrochemical
reactions. Aluminum and magnesium are the primary anodizing bath contaminants. A small amount of
aluminum (0.39 g/L) is required for the aluminum anodizing process to occur. After six weeks of RETEC®
VS-P2MF-01-02 viii
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operation, the purified chromic acid anodized solution maintained a relatively steady chemical and contaminant
composition similar to the anodizing solution at the time of RETEC® start-up. The buildup of process
contaminants in the anodizing solution was slowed, while the contaminant level in the catholyte increased
dramatically, showing a contamination transfer across the polymeric membrane.
Sampling Week
0 - Baseline
1 - Baseline
2 - Baseline
3 - Baseline
4 - Baseline
5 - Baseline
6 - Operational
7 - Operational
8 - Operational
9 - Operational
10- Operational
11- Operational
16- 1Q
Hexavalent
Chromium
(by titration)
g/L
Anolyte /
Catholyte
48.0/NA
48.0/NA
48.1/NA
47.5/NA
50.5/NA
51.5/20.6
52.6/21.3
52.9/22.5
53.5/36.1
53.8/41.5
Trivalent
Chromium
(by titration)
g/L
Anolyte /
Catholyte
<1.1/NA
<1.1/NA
<1.1/NA
<1.1/NA
<1.1/NA
<1. 1/<1.1
<1. 1/<1.1
<1. 1/<1.1
<1. 1/<1.1
<1.1/1.7
Total
Chromium
(by ICP-AES)
g/L
Anolyte /
Catholyte
49.0/NA
46.0/NA
42.0/NA
43.0/NA
50.0/NA
46.0/18.0
44.0/20.0
44.0/21.0
48.0/34.0
46.0/42.0
Total
Aluminum
(by ICP-AES)
g/L
Anolyte /
Catholyte
3.6/NA
3.7/NA
3.8/NA
4.0/NA
4.5/NA
4.5/0.1
4.1/2.0
4.1/3.2
4.6/3.8
4.4/5.4
Total
Magnesium
(by ICP-AES)
g/L
Anolyte /
Catholyte
0.27/NA
0.31/NA
0.25/NA
0.26/NA
0.32/NA
0.32/0.09
0.29/0.12
0.22/0.15
0.24/0.20
0.21/0.25
Thanksgiving holiday - no samples collected this week
52.7/51.6
NA
<1. 1/<1.1
NA
50.0/48.0
52.5/50.5
4.9/6.4
5.4/7.5
0.24/0.28
0.26/0.31
Titration = Standard sodium thiosulfate titration, 1999 Metal Finishing Guidebook, Vol. 97, No. 1, Control,
Analysis, and Testing Section - Chemical Analysis of Plating Solutions, Charles Rosenstein and Stanley
Hirsch, Table VIII - Test Methods for Electroplating Solutions, page 538.
ICP-AES = Inductively Coupled Plasma-Atomic Emission Spectrometry (EPA SW-846 Method 601 OB)
NA = Not Applicable
Table i. Summary of Key Analytical Data
Oxidation of Trivalent Chromium to Hexavalent Chromium. The oxidation of trivalent chromium to
hexavalent chromium in the anolyte and the transfer of hexavalent chromium across the polymeric membrane
from the catholyte to the anolyte by the RETEC® unit is marketed as one of the beneficial conversions performed
by the electrochemical process. However, as can be seen in Table i, trivalent chromium levels were never above
background levels in the anolyte; therefore, there was no quantifiable oxidation to hexavalent chromium. A slight
increase in hexavalent chromium levels in the anolyte was observed, but since DVI adds chromic acid to the
anodizing bath on a regular basis, this increase in hexavalent chromium concentration can not be definitively
attributed to the RETEC® electrolytic reaction. Hexavalent chromium levels measured by titration that are higher
than total chromium levels measured by ICP-AES are due to uncertainties inherent in the precision of these two
different analytical methods.
Contaminant Removal. Removal of the primary contaminants of the chromic acid anodize bath solution,
aluminum and magnesium, are shown in Table ii. For the Baseline Mode, the average aluminum increase in the
anolyte was 0.180 g/L per week. The average magnesium increase in the anolyte was 0.010 g/L per week.
During the Operational Mode, aluminum and magnesium levels in the anolyte remained relatively stable, while
the catholyte showed an overall increase of 6.32 g/1 of aluminum. The total volume of catholyte solution at the
end of the verification test was 392 gallons (150 gallons in the clarifier + 30 gallons in the RETEC® cell and
piping + 212 total gallons of catholyte overflow collected during the test). Multiplying the aluminum
contamination increase in the catholyte by the total catholyte volume gives an overall removal of 9,378 grams of
aluminum from the anolyte solution over the six week test period (6.32 g/1 x 392 gallons x 3.7854 liters/gallon =
VS-P2MF-01-02
IX
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9,378 grams). The increase in magnesium contamination of the catholyte was less pronounced, showing an
overall increase of 0.19 g/1. Multiplying the magnesium contamination increase in the catholyte by the total
catholyte volume gives an overall removal of 282 grams of magnesium from the anolyte solution over the six
week test period (0.19 g/1 x 392 gallons x 3.7854 liters/gallon = 282 grams). The RETEC® unit proved to be an
adequate technology for removing aluminum contamination from the chromic acid anodize solution at DVI;
however, the unit was not able to completely arrest the contamination rise in the anodizing bath. Since the six-
cell model installed at DVI is the smallest RETEC® unit made by USFilter, it is possible that a larger unit may
solve this problem. However, since the RETEC® unit was turned on when the anodizing bath was within 1.6 g/L
of its upper limit for aluminum, the purification system was unable to prevent the anodizing bath from reaching
the upper contamination limit triggering disposal of the anodizing bath. It can be concluded that the RETEC®
system extended the anodizing bath life by slowing the contamination build-up rate, but due to the relatively short
verification test period, the length of this extension could not be determined.
Anolyte
Aluminum
Magnesium
Baseline Mode
Operational Mode
Baseline Mode
Operational Mode
Catholyte
Aluminum
Magnesium
Operational Mode
Operational Mode
Start
(g/L)
3.6
4.5
0.27
0.32
End
(g/L)
4.5
4.9
0.32
0.24
Change
(g/L)
+0.9
+0.4
+0.05
-0.08
Average Weekly Increase
(g/L)
+0.180
+0.067
+0.010
-0.0133
0.085
0.087
6.40
0.28
+6.32
+0.19
+1.053
+0.0317
Table ii. Contaminant Removal
Energy Use. Energy requirements for operating the RETEC® unit at DVI include electricity for the anolyte and
catholyte pumps and the system rectifier. Electricity use was determined to be 6,366 kWh/day, based on
continuous operation of the system.
Waste Generation. A waste generation analysis was performed using operational data collected during the
verification test period, and historical records from DVI. Waste generation data normalized to the amount of
work processed over the verification test period showed an anodizing bath waste generation reduction of about 54
percent when the RETEC® system was in use. Implementation of the RETEC® Model SCP-6 extended the life of
the anodizing bath, thus generating less chromic acid waste. However, some of this waste reduction is offset by
chromic acid waste generated by the RETEC® system. The net reduction of concentrated waste generated from
the chromic acid anodizing process when the purification system was in use is thus reduced to 46 percent.
Hexavalent Chromium Air Emissions. Air emissions from the DVI anodizing bath/RETEC unit were tested for
hexavalent chromium. The aim of this testing was to check to see if the RETEC unit contributed to the
concentration of airborne hexavalent chromium in the DVI facility. Air monitoring was conducted in both the
Baseline and Operational phases of the verification test. The RETEC system exhibited a slight increase in the
overall hexavalent chromium air emissions to the DVI facility. Air monitoring results indicated an average
process hexavalent chromium emission increase of 0.124 |jg/m3. Personal monitoring during the verification test
was performed; however, the samples became contaminated with hexavalent chromium from routine paint filter
change-out maintenance operations, so the results had to be discarded. Process emission readings during the
operational phase of the RETEC® verification test were well within all applicable regulatory and suggested
exposure limits.
Operating and Maintenance Labor. Operating and maintenance (O&M) labor requirements for the RETEC®
Model SCP-6 were monitored during testing. The O&M labor requirements for the equipment were observed to
be 2.8 hrs/wk. Accounting for savings in reduced labor associated with anodizing bath chemical additions, the
RETEC® system O&M labor averages about 135 labor hours per year. O&M tasks performed during the
x
VS-P2MF-01-02
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verification test included daily inspections of the unit, recording of system parameters, and additions of chromic
acid flakes to the clarifier to maintain the catholyte pH below 2.
Cost Analysis. A cost analysis of the RETEC® Model SCP-6 was performed using current operating costs and
historical records from DVI. The installed capital cost (1993) of the unit was $35,230 (includes $33,630 for the
system and $1,600 for installation costs). The annual cost savings associated with the unit is $8,288. The
projected payback period is 4.2 years.
SUMMARY
The test results show that the RETEC® Model SCP-6 does provide an environmental benefit by extending the bath
life of the chromic acid anodize solution, thereby reducing the amount of liquid wastes produced by the anodizing
operation without removing the required anodizing constituents of the bath. The economic benefit associated
with this technology is primarily in reduced waste disposal costs associated with the life extension of the
anodizing bath. Process emission increases of hexavalent chromium during the operation of the RETEC® unit are
negligible. As with any technology selection, the end user must select appropriate bath maintenance equipment
and chemistry for a process that can meet their associated environmental restrictions, productivity, and anodizing
requirements.
Original signed by:
E. Timothy Oppelt
Original signed by:
Donn Brown
E. Timothy Oppelt
Director
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Donn W. Brown
Manager
P2 Metal Finishing Technologies Program
Concurrent Technologies Corporation
NOTICE: EPA verifications are based on evaluations of technology performance under specific,
predetermined criteria and appropriate quality assurance procedures. EPA and CTC make no expressed or
implied warranties as to the performance of the technology and do not certify that a technology will always
operate as verified. The end user is solely responsible for complying with any and all applicable federal,
state, and local requirements. Mention of commercial product names does not imply endorsement.
VS-P2MF-01-02
XI
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TABLE OF CONTENTS
1.0 INTRODUCTION 1
2.0 DESCRIPTION OF CHROMIC ACID ANODIZE BATH SOLUTION
PURIFICATION SYSTEM 1
2.1 Anodize Bath Purification Equipment 1
2.2 Test Site Installation 3
2.3 Operating Flow 4
3.0 METHODS AND PROCEDURES 6
3.1 Test Objectives 6
3.2 Test Procedure 8
3.2.1 System Set-Up 8
3.2.2 Testing 8
3.3 Quality Assurance/Quality Control 8
3.3.1 Data Entry 8
3.3.2 Sample Collection and Handling 9
3.3.3 Calculation of Data Quality Indicators 9
3.3.3.1 Precision 9
3.3.3.2 Accuracy 10
3.3.3.3 Completeness 10
3.3.3.4 Comparability 10
3.3.3.5 Representativeness 11
3.3.3.6 Sensitivity 11
4.0 VERIFICATION DATA 12
4.1 Analytical Results 12
4.2 Process Measurements 13
4.3 Production Data 15
4.4 Other Data 16
4.5 Hexavalent Chromium Air Monitoring 16
5.0 EVALUATION OF RESULTS 16
5.1 Oxidation of Trivalent Chromium to Hexavalent Chromium 16
xu
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5.2 Contaminant Removal 17
5.3 Mass Balance 18
5.4 Hexavalent Chromium Air Monitoring Results 19
5.5 Energy Use 20
5.6 Operating and Maintenance Labor Analysis 21
5.7 Chemical Use Analysis 22
5.8 Waste Generation Analysis 23
5.9 Cost Analysis 24
5.10 Project Responsibilities/Audits 25
6.0 REFERENCES 26
LIST OF FIGURES
Figure 1. RETEC® Chromic Acid Anodize Bath Solution Purification at DVI, Inc ..................... 2
Figure 2. RETEC® SCP- 6 System [[[ 3
Figure 3. RETEC Chromium Purification Cell Reactions [[[ 5
LIST OF TABLES
Table 1. Test Objectives and Related Test Measurements Conducted During the 7
Verification of the USFilter RETEC® Model SCP-6 7
Table 2. Laboratory Methodology Information 12
Table 3. Summary of Analytical Results (RETEC® & Bath) 13
Table 4. Summary of Process Measurements 14
Table 5. DVI Production (Ah required for anodizing) 15
Table 6. Other Data Collected During Verification 16
Table 7. Contaminant Removal 17
Table 8. Summary of Analytical Results (Rinse & Flake) 19
Table 9. Air Monitoring Results - Baseline Phase 20
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Table 12. Results of Waste Generation Analysis 23
Table 13. Annual Costs/Savings 25
LIST OF APPENDICES
APPENDIX A: Precision Calculations A-l
APPENDIX B: Accuracy Calculations B-l
APPENDIX C: Representativeness Calculations C-1
xiv
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1.0 INTRODUCTION
The RETEC® Model SCP-6 (RETEC® unit) is an electrochemical purification system for
recycling spent chromic acid anodized bath solution. Chromic acid anodizing is
performed on various aluminum parts in one of two independent parts processing lines: a
27-foot or a 62-foot tank. The verification test evaluated the ability of the RETEC unit
to purify the chromic acid anodize bath solution of process contaminants in the 27 foot
chromic anodizing tank. It was tested by CTC under the U.S. Environmental Protection
Agency (EPA) Environmental Technology Verification Program for P2 Metal Finishing
Technologies (ETV-MF). The purpose of this report is to present the results of the
verification test.
The RETEC® unit was tested to evaluate and characterize the operation of the
electrochemical purification system through measurement of various process parameters.
Testing was conducted at DV Industries, Inc. (DVI) in Lynwood, California. DVT
anodizes a wide range of aluminum parts for the aerospace, military, and commercial
industries.
2.0 DESCRIPTION OF CHROMIC ACID ANODIZE BATH SOLUTION
PURIFICATION SYSTEM
2.1 Anodize Bath Purification Equipment
A diagram of the RETEC® unit is shown in Figure 1. The RETEC® Model SCP-6
consists of a rectifier, a clarifier to remove metal hydroxides that are formed in the
catholyte as acids are purified and recovered, and an electrolytic cell. The electrolyzer
box is fabricated of polyvinyl chloride and is supplied with inlet, outlet, and drain
connections and valves. The cell consists of a series of anodes and cathodes. The
individual lead anodes are contained within separate anode chambers. The front and back
sides of the anode chambers have diaphragms of Elramix™, a porous, polymeric
membrane, separating the anolyte and catholyte compartments. Elramix™, manufactured
by ELTECH International Corporation, was selected as the separator of choice after an
extended evaluation of a wide variety of commercial materials having properties required
for use as cell separators. Titanium mesh cathodes, which are easily removed from the
cell, are placed between each anode chamber. The anodes and cathodes are connected to
copper bus bars located on opposite sides of the cell box. The electrolyzer can operate
with a full complement of anode chambers or any fewer numbers depending on capacity
requirements. The cell is equipped with an air sparging system to prevent metals and
metal hydroxides formed in the catholyte from settling in the cell. However, it was
determined by DVT that the formation of solids could be controlled by maintaining the
pH of the catholyte <2 with additions of chromic acid, and therefore, the air sparging
system was not used at DVT.
A thermo-sensor is included with the electrolyzer to shut off the rectifier if the
temperature of the liquid being treated exceeds the pre-set limit. A thermo-controller
resets the system. The RETEC® electrolyzer is also supplied with a manifold located
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beneath the electrolyzer box that hydraulically connects each anode compartment to the
anolyte reservoir. The anolyte feed manifold is located beneath the cathode bus bar.
Solution from the anodizing tank is pumped into the anode frames through the anolyte
feed manifold. The anodizing solution is returned by gravity to the anodizing tank from
the anolyte reservoir.
RETEC® SEPARATED CELL PURIFICATION (SCP) SYSTEM
Chromic Acid Anodize Bath Solution Purification at DVI, Inc.
Clarifier Overflow
D = Anolyte D = Catholyte D = Waste Products
= Pump XI = Valve
Figure 1. RETEC® Chromic Acid Anodize Bath Solution Purification
at DVI, Inc.
The RETEC® electrolyzer sits on a steel chassis, which mounts onto a stand to provide
the proper height when installed at the anodizing line. The stand contains shelves for
mounting the liquid feed pumps. Figure 2 shows a picture of a six-compartment acid
purification cell (RETEC® SCP-6), clarifier and rectifier similar to the one verified at
DVI.
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Figure 2. RETEC® SCP-6 System
Utility requirements for the RETEC® Model SCP-6 at DVI include:
• Electricity - Rectifier: 460 VAC, 60 Hz, three-phase SCR
• Electricity - Anolyte Pump: 115 VAC, 50/60 Hz, 1/25 HP, 5 gpm
• Electricity - Catholyte Pump: 115 VAC, 50/60 Hz, 1/16 HP, 10 gpm
2.2 Test Site Installation
The metal finisher selected for testing is DVI in Lynwood, California. Established in
1957, the 135,000 square foot facility has one of the nation's largest anodizing
departments. They serve a variety of customers, with a large majority of the work
dedicated to the aerospace, military, and commercial industries.
The Lynwood plant utilizes a USFilter RETEC® Model SCP-6 Separated Cell
Purification System installed on the 27-foot, 10,000 gallon chromic acid anodizing (type
I) line. The Model SCP-6 has been operating successfully in purification mode since
1995. Anodizing bath solution is purified of tramp metals and trivalent chromium, and
the catholyte, which is also anodizing bath solution, is circulated through the RETEC®
system, resulting in the recovery of hexavalent chromium for reuse in the anodizing bath.
DVI has not experienced any degradation in plating quality since the installation of the
RETEC® unit. The DVT anodizing line uses a manually operated rack system. Materials
anodized on the line consist of various grades of aluminum, primarily 7075, 2024, 2219,
6061, and 7050. Parts first go through an alkaline clean, a caustic etch, then a
deoxidizing tank. Subsequently, they go to the anodizing step, and finally the parts are
sealed. Each process step is followed by a single-stage flowing rinse. Since the
anodizing bath operates at an elevated temperature, there is some evaporation from the
-------
tank. On occasion, DVI will add water and/or chromic acid flakes to the bath to maintain
the proper anodizing bath chemical parameters.
The solution from the anodizing bath was re-circulated through the anolyte compartment
of the cell at a rate of about 1.5 gpm. The cell applies approximately 200A @ 3 VDC for
the electrolytic reaction to take place. Trivalent chrome is oxidized to hexavalent
chrome, and at the same time, tramp metals are rejected through the Elramix™ separator
into the catholyte compartment. Anodizing solution also acts as the catholyte and is
pumped continuously through the catholyte compartment at a rate of about 4 gpm.
Hexavalent chrome in the catholyte passes through the Elramix™ into the anolyte
compartment - this gives a substantial recovery of the hex chrome from the catholyte at
the same time.
The chromic acid used at this facility is created by mixing tap water with chromic acid-
flake, which is sold by Van Waters & Rogers, Inc., a company located in Los Angeles,
California. The Material Safety Data Sheet (MSDS) for this product can be found in the
test plan [Ref. 2]. The concentration of chromic acid is controlled based on free and total
chrome concentration, which is determined twice a week by a sodium thiosulfate titration
method performed by the DVT process chemists. When measurements indicate that the
chromium concentration is approaching the lower recommended operating level,
additional chromic acid flakes are added to the anodizing bath.
Fumetrol 140 Mist Suppressant is also added to the bath to act as a wetting agent to lower
the surface tension of the bath. Keeping the surface tension of the anodizing bath in the
prescribed operating limits keeps the hexavalent chromium air emissions to a minimum.
The Fumetrol 140 Mist Suppressant is also sold to DVT by Van Waters & Rogers, Inc., of
Los Angeles, California. The MSDS for this product can be found in the test plan [Ref.
2]. The concentration of Fumetrol 140 Mist Suppressant is controlled based on surface
tension, which is determined twice a week by stalagmometer measurements performed by
the DVI process chemists. When measurements indicate that the surface tension is
approaching the upper recommended operating limit, additional Fumetrol 140 Mist
Suppressant is added to the anodizing bath.
When the catholyte reaches the aluminum saturation limit (approximately every three
months), two-thirds (100 gallons) of the clarifier is drained off and sent for waste
disposal. The catholyte is then recharged with a fresh mixture of chromic acid.
2.3 Operating Flow
Anodizing solution is recirculated between the anolyte section of the RETEC® cell and
the anodizing tank. During this process, trivalent chromium in the solution is oxidized to
hexavalent chromium, and metal cations in solution are transported through the cell
separator to the catholyte section of the cell. The rate of trivalent chromium oxidation
and the transfer rate of metal cations are related to the operating conditions. The
oxidation rate of trivalent chromium will vary with cell current, and will be greater at
high current and high trivalent chromium concentration. The anolyte to catholyte transfer
-------
rate of metal cations will depend on the species of cation present in solution, cation
concentration, and the pH of the catholyte. Process operating conditions will vary and
will depend upon the type and degree of contamination of the anodizing bath.
Catholyte solution is circulated between the catholyte section of the RETEC® cell and the
clarifier. The catholyte pH is controlled by the addition of anodizing solution or straight
chromic acid to the clarifier. Hexavalent chromium in the catholyte is transferred
through the cell separator to the anolyte side of the cell and then to the anodizing tank.
Metal impurities in the chemicals added to the clarifier tank for pH control, and those
impurities that are transferred from the anolyte through the cell separator into the
calholyte, all accumulate in the catholyte solution.
Disposal of the catholyte saturated with tramp metal impurities is required when
adjusting the catholyte operating conditions by pH addition is no longer possible. The
tramp metal cations precipitate out as their respective hydroxides, which are then
separated from solution in the clarifier. This catholyte saturation timeframe varies based
on process chemistry, RETEC® operating parameters, contamination build-up rate, and
workload, but historically occurs about once every three months.
The diagram in Figure 3 illustrates the reactions that typically take place in the RETEC®
cell. While this simplified diagram shows only one anode chamber, the Model SCP-6
used at DVI contains six anode chambers.
RETEC CHROME PURIFICATION (CP) SYSTEM
Chromium Purification Cell Reactions
ELRAMIX™ Cell Separator
<+) Anode
*s
^
^
Cr+3 ^ CrO4-2
1 — |
*
M+n ^ M(OH)n
Cr+3 ^ Cr(OH)3
X*
Cathode
Anolyte
Chamber
Catholyte
Chamber
Figure 3. RETEC® Chromium Purification Cell Reactions
At DVI, the RETEC® cell is cleaned on a quarterly basis. This time period was selected
out of convenience and does not necessarily reflect the required frequency of cleaning.
-------
The RETECR unit operating manual suggests that users monitor the physical condition
and contamination buildup on the cathodes to determine when the unit requires cleaning.
When a high level of contamination buildup on the cathodes is evident, the unit requires
cleaning. The contamination rate varies from site to site, depending on factors such as
process load and contaminant characteristics. The cleaning schedule is determined
through operating experience. The unit was not cleaned during the six weeks of
RETEC®operation. Cleaning the RETEC® cell produces about 30 gallons of chromic
acid waste.
3.0 METHODS AND PROCEDURES
3.1 Test Objectives
The following is a summary of project objectives. Under normal system operating
conditions for the installation at DVI:
• Prepare a material balance for certain anodizing bath constituents and contaminants in
order to:
1) Evaluate the ability of the RETEC® unit to oxidize trivalent chromium formed
in the bath during the anodizing process.
2) Evaluate the ability of the RETEC® unit to remove aluminum and other tramp
metals from the process bath that build up during the anodizing process.
3) Evaluate the ability of the RETEC® unit to recover chromic acid from the
catholyte solution.
• Determine the cost of operating the chromic acid anodize bath solution purification
system for the specific conditions encountered during testing by:
1) Determining labor requirements needed to operate and maintain the RETEC®
unit.
2) Determining the quantity of energy consumed by the RETEC® unit during
operation.
3) Determining other costs associated with operation of the RETEC® unit.
• Quantify the environmental benefit by performing an analysis of waste generation,
which compares the quantity of waste generated before and after the installation of
the RETEC® unit. Data collected to satisfy the test objectives are shown in Table 1.
-------
Test Mode
Baseline:
(RETEC®
Off)
Operational:
(RETEC®
On)
Test Objectives
Determine the build-up rate of contamination in the
chromic acid anodize bath solution.
Monitor and record anodizing process operational
parameters.
Evaluate the ability of the RETEC " unit to oxidize trivalent
chromium formed in the bath during the anodizing process.
Evaluate the ability of the RETEC " unit to remove
aluminum and other tramp metals from the process bath
that build up during the anodizing process.
Evaluate the ability of the RETEC " unit to recover chromic
acid from the catholy te solution.
Monitor and record anodizing process and RETEC " system
operational parameters.
Determine labor requirements needed to operate and
maintain the RETEC® unit.
Determine the quantity of energy consumed by the
RETEC® unit during operation.
Determine the cost of operating the chromic acid anodize
bath purification system for the conditions encountered
during testing
Quantify /identify the environmental benefit.
Test Measurements
Chemical characteristics of chromic acid anodize bath solution.
Chemical characteristics of upstream and downstream rinse tank water.
Volume and physical characteristics of chromic acid anodize bath solution.
Volume and physical characteristics of anodizing process rinse tank water.
Quantity and price of chemical/water additions to the anodizing bath.
Production throughput for anodizing bath.
Worker exposure to hazardous air emissions.
Volume of anodizing solution and flow rate through RETEC " unit.
Chemical characteristics of chromic acid anodize bath solution (anolyte).
Volume of anodizing solution and flow rate through RETEC " unit.
Chemical characteristics of chromic acid anodize bath solution (anolyte).
Volume, flowrate and chemical characteristics of catholyte solution.
Volume and chemical characteristics of the waste products.
Volume of anodizing solution and flow rate through RETEC " unit.
Chemical characteristics of chromic acid anodize bath solution (anolyte).
Volume, flow rate and chemical characteristics of catholyte solution.
Volume and chemical characteristics of the waste products.
Volume and physical characteristics of anodizing solution (anolyte).
Volume and physical characteristics of chromic acid catholyte solution.
Volume and physical characteristics of anodizing process rinse tank water.
Quantity and price of chemical/water additions to the anodizing bath.
Quantity and price of chemical/water additions to the RETEC® system.
Production throughput for anodizing bath.
Worker exposure to hazardous air emissions.
O&M labor required during test period.
Quantity of energy used by liquid transfer pumps (anolyte and catholyte).
Quantity of energy used by RETEC® electrochemical cell (rectifier).
Costs of O&M labor, materials, and energy required during test period.
Quantity and price of make-up and process control chemicals/water added during
testing.
Review historical waste disposal records and compare to current practices.
Table 1. Test Objectives and Related Test Measurements Conducted During the
Verification of the USFilter RETEC® Model SCP-6
-------
3.2 Test Procedure
3.2.1 System Set-Up
Prior to testing, the RETEC® cell was turned off, drained and cleaned, and the
clarifier was emptied according to the manufacturer's instructions [Ref. 1]. Five
weeks of anodizing and sampling were completed with the RETEC® unit turned
off. At the end of the five-week "Baseline" period, the RETEC® cell and clarifier
were filled with freshly mixed chromic acid solution to act as the catholyte, and
the RETEC® unit was started. Weekly sampling continued, once the unit was
operating, for another six weeks with an anolyte flow rate of about 2.0 gpm. This
flow rate is in the middle of the target operating range used by DVT.
3.2.2 Testing
The RETEC® unit was tested in accordance with the verification test plan [Ref 2.
Testing was conducted during two distinct test periods:
During the first test period (Baseline Mode), the unit was turned off and weekly
sampling occurred under normal production conditions at DVI. Contamination
build-up data and process operating measurements were gathered during this five-
week period.
During the second test period (Operational Mode), the RETEC® unit was turned
on and operated under normal production conditions. Weekly samples were taken
to determine contaminant removal rate from the anodizing bath and the recovery
rate of hexavalent chromium from the process.
As indicated in section 2.2, when the catholyte reaches the aluminum saturation
limit (approximately every 90 days), two-thirds (100 gallons) of the clarifier is
drained off and sent for waste disposal. The catholyte is then recharged with a
fresh mixture of chromic acid. The Operational Mode commenced with a fresh
mixture of chromic acid catholyte. Therefore, during this project, Operational
Mode testing was conducted during the 1st quarter of the semi-annual operating
cycle. Clarifier samples are scheduled to be collected in the final quarter of the
operating cycle as well, and an revision of the Verification Report stating the
volume and composition of this RETEC waste stream will be issued when this
catholyte lifespan data is obtained.
3.3 Quality Assurance/Quality Control
3.3.1 Data Entry
Sampling events, process measurements, and all other data were recorded by the
ETV-MF Project Manager or his representative on pre-designed forms provided
in the verification test plan [Ref 2].
-------
3.3.2 Sample Collection and Handling
Prior to the verification test, sampling ports were installed on the anolyte and
catholyte lines of the RETEC® unit. Polyethylene tubes were connected to these
two sampling ports and directed into 500-ml High Density Polyethylene (HDPE)
aqueous sample containers. 500 ml grab samples were taken with a 1000 ml
polypropylene sampling beaker from the anodizing bath, rinse tanks and waste
drums. During sampling, the sample collection containers were kept cool by
placing them in a cooler containing ice.
All aqueous samples were collected in the HDPE containers at weekly intervals
over an eleven-week period. At the end of each weekly sampling event, the
HDPE containers were labeled and stored in a cooler containing ice, awaiting
shipment to the analytical laboratories.
A sample of the chromic acid-flake (MSDS # OZ4824) supplied by Van Waters
& Rogers, Inc. of Los Angeles, California, was collected from its original
shipping container. These samples were labeled and stored prior to shipment h a
cooler containing ice.
Samples shipped to the analytical laboratories were packed in coolers containing
"blue ice." A laboratory courier picked up and delivered the samples within six
hours of sampling. All shipments were secured with strapping tape and security
seals and accompanied by chain of custody forms.
3.3.3 Calculation of Data Quality Indicators
Data reduction, validation, and reporting were conducted according to the
verification test plan [Ref 2] and the ETV-MF Quality Management Plan (QMP)
[Ref 3]. Calculations of data quality indicators are discussed in this section.
3.3.3.1 Precision
Precision is a measure of the agreement or repeatability of a set of
replicate results obtained from duplicate analyses made in the laboratory
under identical conditions. To satisfy the precision objectives, the
replicate analyses must agree within defined percent deviation limits,
expressed as a percentage, Relative Percent Difference (RPD), calculated
as follows:
RPD = {(|Xi - X2|)/(Xi + X2)/2} x 100% =
|X,-X2|
2
_+X2)
where,
Xi = larger of the two observed values
X? = smaller of the two observed values
xlOO%
-------
The analytical laboratories performed a total of 75 precision evaluations
on aqueous samples. All of the results were within the precision limits
identified in the verification test plan [Ref 2]. The results of the precision
calculations are summarized in Appendix A
3.3.3.2 Accuracy
Accuracy is a measure of the agreement between an experimental
determination and the true value of the parameter being measured.
Analyses with spiked samples were performed to determine percent
recoveries as a means of checking method accuracy. The percent
recovery, expressed as a percentage, is calculated as follows:
(SSR-SR)"
V ' xlOO%
SA
where:
SSR = spiked sample result
SR = sample result (native)
SA = the concentration added to the spiked sample
Quality Assurance (QA) objectives are satisfied for accuracy if the
average recovery is within selected goals. The analytical laboratories
performed 75 accuracy evaluations on aqueous samples. All results were
within the limits identified in the verification test plan [Ref 2]. The
results of the accuracy calculations are summarized in Appendix R
3.3.3.3 Completeness
Completeness is defined as the percentage of measurements judged to be
valid compared to the total number of measurements made for a specific
sample matrix and analysis. Completeness, expressed as a percentage, is
calculated using the following formula:
Completeness = Valid Measurements x 100%
Total Measurements
QA objectives are satisfied if the percent completeness is 90 percent or
greater. All measurements made during this verification project were
determined to be valid and completeness was 100 percent. Therefore the
completeness objective was satisfied.
3.3.3.4 Comparability
Comparability is a qualitative measure designed to express the confidence
with which one data set may be compared to another. Sample collection
and handling techniques, sample matrix type, and analytical method all
affect comparability. Comparability was achieved during this verification
10
-------
test by the use of consistent methods during sampling and analysis and
traceability of standards to a reliable source.
3.3.3.5 Representativeness
Representativeness refers to the degree to which the data accurately and
precisely represent the conditions or characteristics of the parameter being
tested. For this verification project, one field duplicate sample was
collected from each sample location and sent to the laboratory for analysis.
Representativeness was calculated as an RPD of these field duplicates.
The results of these calculations are shown in Appendix C.
3.3.3.6 Sensitivity
Sensitivity is the measure of the concentration at which an analytical
method can positively identify and report analytical results. The
sensitivity of a given method is commonly referred to as the detection
limit. Although there is no single definition of this term, the following
terms and definitions of detection were used for this project.
Instrument Detection Limit (DDL) is the minimum concentration that can
be differentiated from instrument background noise; that is, the minimum
concentration detectable by the measuring instrument.
Method Detection Limit (MDL) is a statistically determined
concentration. It is the minimum concentration of an analyte that can be
measured and reported with 99 percent confidence that the analyte
concentration is greater than zero, as determined in the same or a similar
sample matrix. In other words, this is the lowest concentration that can be
reported with confidence. It may be determined by an DDL. The MDLs
for this verification project are shown in Table 2.
Method Reporting Limit (MRL) is the concentration of the target analyte
that the laboratory had demonstrated the ability to measure within
specified limits of precision and accuracy during routine laboratory
operating conditions. [This value is variable and highly matrix dependent.
It is the minimum concentration that will be reported without
qualifications by the laboratory].
11
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Critical
Measurements
Hexavalent
Chrome
Trivalent
Chrome
Hexavalent
Chrome
Trivalent
Chrome
Selected Metals
(Cr, Al & Mg)
Selected Metals
(Cr, Al & Mg)
Matrix
Aqueous
(Bath/
RETEC®)
Aqueous
(Bath/
RETEC®)
Aqueous
(Rinsewater)
Aqueous
(Rinsewater)
Aqueous
Solid
(Cr Flake)
Method
See Note 1
See Note 1
SM 3500 Cr D
SM 3500 Cr D
SW-846
3010A/6010B
SW-846
3050B/ 6010B
Reporting
Units
g/L
g/L
ug/L
ug/L
ug/L
mg/Kg
Method of
Determination
Titration
Titration
Colorimetric
Colorimetric
ICP-AES
ICP-AES
MDL
UOg/L
l.lOg/L
10 Hg/L
5 Hg/L
2 -100 ng/L
2 -20 mg/Kg
MRL
2.00 g/L
2.00 g/L
100 ng/L
100 ng/L
10 -100 Hg/L
2 -20 mg/Kg
Note 1: Standard sodium thiosulfate titration was used to determine the hexavalent and trivalent chromium
concentration. These procedure were taken directly from the 1999 Metal Finishing Guidebook, Vol. 97,
No. 1, Control, Analysis, and Testing Section - Chemical Analysis of Plating Solutions, Charles Rosenstein
and Stanley Hirsch, Table VIII - Test Methods for Electroplating Solutions, page 538.
SM = Standard Methods for the Examination of Water and Wastewater, 20th Edition, January 15,1999.
ICP-AES = Inductively Coupled Plasma-Atomic Emission Spectrometry (EPA SW-846 Method 601 OB)
Table 2. Laboratory Methodology Information
4.0 VERIFICATION DATA
4.1 Analytical Results
A complete summary of analytical data for the anolyte and catholyte is presented in
Table 3. Samples were collected over an eleven-week period and analyzed for
hexavalent and trivalent chromium, total chromium, aluminum and magnesium. During
the five-week Baseline Mode, samples were collected from the chromic acid anodize bath
solution as grab samples directly from the anodizing bath. During the Operational Mode,
samples were taken from the sampling ports installed on the RETEC® anolyte and
catholyte liquid transfer lines. The "1Q" samples are post-verification test samples from
the anolyte and catholyte lines of the RETEC® unit, collected at the end of the 1st quarter
of the catholyte operating cycle, 11 weeks after the RETEC® unit was turned on, and just
prior to disposal of the anodizing bath. Anodizing bath disposal was required because
aluminum contamination reached the bath's upper limit.
The primary contaminants of the chromic acid anodizing bath solution are aluminum and
magnesium. The values for these parameters during the Baseline Mode represent
contaminant build-up during normal production conditions. During the Operational
Mode, the RETEC unit was placed in operation to purify the chromic acid anodize bath
solution. The normal production conditions observed in the Baseline Mode were
maintained in the Operational Mode.
12
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Sampling Week
0- Baseline
1- Baseline
2- Baseline
3- Baseline
4- Baseline
5- Baseline
6- Operational
7- Operational
8- Operational
9- Operational
10- Operational
11- Operational
16- 1Q
Hexavalent
Chromium
(by titration)
g/L
Anolyte /
Catholyte
48.0/NA
48.0/NA
48.1/NA
47.5/NA
50.5 /NA
51.5/20.6
52.6/21.3
52.9/22.5
53.5/36.1
53.8/41.5
Trivalent
Chromium
(by titration)
g/L
Anolyte /
Catholyte
< 1.1 /NA
< 1.1 /NA
< 1.1 /NA
< 1.1 /NA
< 1.1 /NA
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Test Mode/
Sample Date
Anodizing
Bath
Volume,
gallons
Anodizing
Bath
Surface
Tension
dynes/cm
Anodizing
Bath
(Anolyte)
Temp.
°C
Anodizing
Bath
PH
Anolyte
Flow
Rate
gpm
RETEC®
Amp-
hours Ah
Catholyte
Temp.
°C
Catholyte
PH
Catholyte
Flow
Rate
gpm
Baseline Mode
09-14-00
09-21-00
09-28-00
10-05-00
10-12-00
10-19-00
Average
9,240
9,320
9,320
9,400
9,400
9,320
9,333
24.6
20.7
19.6
24.8
24.7
24.7
23.2
38.5
36.2
35.9
34.1
34.0
35.3
35.7
0.70
0.55
0.75
1.04
0.69
0.73
0.74
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Operational Mode
10-26-00
11-02-00
11-09-00
11-16-00
11-23-00
11-30-00
Average
9,320
9,240
9,240
9,160
*
9,240
9,240
26.3
26.6
27.3
28.1
*
27.1
27.1
33.3
33.4
34.0
33.3
*
33.2
33.4
0.81
0.81
1.11
0.86
*
0.95
0.91
1.51
1.44
1.69
1.64
*
2.94
1.84
27,594
31,285
34,264
38,744
41,372
43,598
36,143
31.5
31.4
30.7
30.7
*
31.4
31.1
1.08
2.89
1.19
2.52
*
1.12
1.76
4.49
3.78
4.44
2.98
*
4.26
3.99
* Thanksgiving holiday - no monitoring done this week.
NA = Not Applicable
Table 4. Summary of Process Measurements
Anodizing bath volume is maintained by the periodic addition of water to the anodizing
tank by the DVT maintenance personnel. There was only one water addition to the
anodizing bath during the eleven-week verification test period. 160 gallons of water was
added to the anodizing tank during the Baseline Mode on 10-5-00.
Anodizing bath surface tension is required to be maintained below 40 dynes/cm.
Maintaining the surface tension of the chromic acid anodizing bath below this level limits
hexavalent chromium air emissions. In order to maintain the surface tension below the
required limit, DVI maintenance personnel added a total of 17 gallons of Fumetrol 140
Mist Suppressant (MSDS# P14857VS) which is supplied by Van Waters & Rogers, Inc.
of Los Angeles, California. Six gallons were added to the anodizing tank during the
Baseline Mode, and 11 gallons were added during the Operational Mode.
The target anolyte flow rate range specified by USFilter for DVTs RETEC system is 1-3
gpm. The target flow rate for the catholyte is 4 gpm. During operation of the unit,
operators adjust the flow rate of the anolyte and catholyte solutions within the
recommended operating limits. If the anolyte flow is too high, there is an increase in the
bleed-through of anolyte from the anolyte side of the system to the catholyte side,
causing the clarifier to overflow. Clarifier overflow is normally piped back to the
anodizing tank for reintroduction to the anolyte loop, but was disconnected and piped to
temporary storage drums for the duration of the verification test in order to track its
14
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volume. Clarifier overflow averaged about 35 gallons per week with a total of 212
gallons during the six weeks of RETEC operation.
®
Total amp-hours for the RETEC unit is a function of the electricity required to complete
the electrochemical reaction in the cell. The amount of electricity introduced to the
process is controlled by adjusting the voltage cf the RETEC® cell. The amount of voltage
required is dependent on several factors, including the chemical composition and physical
characteristics of the catholyte. To maintain the catholyte in the proper pH for the
reaction to occur, an average of 17 pounds of chromic acid flake was added to the
clarifier each week of the test (total 102 pounds) over the 6 weeks of RETEC® operation.
4.3 Production Data
The RETEC system is connected to the 27-foot chromic acid anodizing tank at DVI.
The anodizing bath can accept parts up to 26'xlO'x5'; however, due to the large quantity
of uniquely sized parts, it was not feasible to measure production volume by square feet
anodized. At DVI, production volume is measured in overall amp-hours for the 27-foot
line. The amp -hours required to anodize parts in the 27- foot line during verification
testing are summarized in Table 5.
Test Mode/
Sample Date
Anodizing Bath
Amp-hours
Baseline
09-14-00
09-21-00
09-28-00
10-05-00
10-12-00
10-19-00
Total Baseline
0
52,834
48,618
41,720
40,863
43,068
227,103
Operational
10-26-00
11-02-00
11-09-00
11-16-00
11-23-00
11-30-00
Total Operational
Total
38,344
38,585
32,371
44,338
39,505
26,936
220,079
447,182
Anodizing Bath Process Load
"\
"N-^^ /\
\
^
123456789 10 11
Sampling Week
Table 5. DVI Production (Ah required for anodizing)
15
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4.4 Other Data
Other data collected during the course of the verification test are summarized in Table 6.
Description
Cost of chromic acid flake
Chromic acid used 3/20/99-1/3/00 - RETEC® off*
Chromic acid used 1/3/00-9/6/00 - RETEC® on*
Chromic acid additions during Baseline Mode
Chromic acid additions during Operational Mode
Cost of Fumetrol 140 Mist Suppressant
Fumetrol 140 used 3/20/99-1/3/00 - RETEC® off*
Fumetrol 140 used 1/3/00-9/6/00 - RETEC® on*
Fumetrol 140 additions during Baseline Mode
Fumetrol 140 additions during Operational Mode
Electricity by cost
Labor cost (loaded rate)
Initial cost RETEC® unit*
Installation cost RETEC® unit*
Value
$1.31perlb
9,010 Ib
8,890 Ib
990 Ibs
760 Ibs
$515/gal
32 gal
31 gal
14 gal
17 gal
$0.09/kWh
$10.00/hr
$33,630 (1993)
$1,600 (1993)
*Data from D VI historical records
Table 6. Other Data Collected During Verification
4.5 Hexavalent Chromium Air Monitoring
Air emissions from the DVI anodizing bath/RETEC unit were tested for hexavalent
chromium. The objective of this testing was to check to see if the RETEC unit
contributed to the concentration of airborne hexavalent chromium in the DVT facility.
Air monitoring was conducted in both the Baseline and Operational phases of the
verification test. During each phase, multiple two-hour samples were collected from a
stationary process emissions monitor as well as a worker breathing zone air monitor for
personal exposure. Personal exposure and process emissions samples were collected in
accordance with appropriate National Institute of Occupational Safety and Health
(NIOSH), and California Air Resources Board (CARB) methods, respectively. Both
types of samples were analyzed according to EPA method 306 for hexavalent chromium.
5.0 EVALUATION OF RESULTS
5.1 Oxidation of Trivalent Chromium to Hexavalent Chromium
The oxidation of trivalent chromium to hexavalent chromium in the anolyte and the
transfer of hexavalent chromium across the polymeric membrane from the catholyte to
the anolyte by the RETEC unit is marketed as one of the beneficial conversions
performed by the electrodialysis process. However, as can be seen in Table 3, trivalent
chromium levels were never above background levels in the anolyte, so there was no
quantifiable oxidation to hexavalent chromium. A slight increase in hexavalent
chromium levels in the anolyte was observed, but since DVT adds chromic acid to the
anodizing bath on a regular basis, this increase in hexavalent chromium concentration can
16
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not be definitively attributed to the RETEC® electrolytic reaction. Increases in catholyte
hexavalent chromium may be attributed to the fact that DVI adds chromic acid flake to
the catholyte to control catholyte pH. Hexavalent chromium levels measured by titration
that are higher than total chromium levels measured by ICP-AES are due to uncertainties
inherent in the precision of these two analytical methods.
5.2 Contaminant Removal
Reduction of the rate of increase of the primary contaminants of the chromic acid anodize
bath solution, aluminum and magnesium, are shown in Table 7. For the Baseline Mode,
the average weekly aluminum increase in the anolyte was 0.180 g/L. The average weekly
magnesium increase in the anolyte was 0.010 g/L. During the Operational Mode,
aluminum and magnesium levels in the anolyte remained relatively stable, while the
catholyte showed an overall increase of 6.32 g/1 of aluminum. The total volume of
catholyte solution at the end of the verification test was 392 gallons (150 gallons in the
clarifier + 30 gallons in the RETEC® cell and piping + 212 total gallons of catholyte
overflow collected during the test). Multiplying the aluminum contamination increase in
the catholyte by the total catholyte volume gives an overall removal of 9,378 grams of
aluminum from the anolyte solution over the six week test period (6.32 g/1 x 392 gallons
x 3.7854 liters/gallon = 9,378 grams). The increase in magnesium contamination in the
catholyte was less pronounced, showing an overall increase of 0.19 g/1. Multiplying the
magnesium contamination increase in the catholyte by the total catholyte volume gives an
overall removal of 282 grams of magnesium from the anolyte solution over the six week
test period (0.19 g/1 x 392 gallons x 3.7854 liters/gallon = 282 grams). The RETEC® unit
proved to be an adequate technology for removing aluminum contamination from the
chromic acid anodize solution at DVI; however, the unit was not able to completely arrest
the contamination rise in the anodizing bath. Since the six-cell model installed at DVI is
the smallest RETEC® unit made by USFilter, it is possible that a larger unit may solve
this problem. However, since the RETEC® unit was turned on when the anodizing bath
was within 1.6 g/L of its upper limit for aluminum, the purification system was unable to
prevent the anodizing bath from reaching the upper contamination limit, triggering
disposal of the anodizing bath. It can be concluded that the RETEC® system extended
the anodizing bath life by slowing the contamination build-up rate, but due to the
relatively short verification test period, the length of this extension could not be
determined.
Anolyte
Aluminum
Magnesium
Baseline Mode
Operational Mode
Baseline Mode
Operational Mode
Catholyte
Aluminum
Magnesium
Operational Mode
Operational Mode
Start
(g/L)
3.6
4.5
0.27
0.32
End
(g/L)
4.5
4.9
0.32
0.24
Change
(g/L)
+0.9
+0.4
+0.05
-0.08
Average Weekly
Increase (g/L)
+0.180
+0.067
+0.010
-0.0133
0.085
0.087
6.40
0.28
+6.32
+0.19
+1.053
+0.0317
Table 7. Contaminant Removal
17
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5.3 Mass Balance
Mass balance calculations are designed to be an accounting of the weights of materials
entering and leaving a processing unit. They help to evaluate how effectively the
sampling and analytical procedures account for certain key parameters.
Initially, this verification test included a planned mass balance exercise to be contained in
the verification report; however, due to specific process design at DVT and technical
constraints, it was determined that a mass balance exercise would not be feasible. Mass
balance calculations typically measure the inputs to a process and compare them with the
outputs to confirm that the totality of all output constituents are equal or close to the input
constituents. This comparison is highly effective in determining the process efficiency
and sampling/analytical accuracy for a single pass processing system such as a filter, or a
multi-pass processing unit such as a membrane with an influent that is stable or exhibits a
known flux in constituents.
At DVI, it is impossible to detect a contaminant differential in the influent and effluent of
the RETEC® system. The unit removes a minute amount of tramp metals and oxidizes an
even smaller amount of trivalent chromium to hexavalent chromium on each pass, but
analytical methods and their inherent limitations on accuracy, precision and resolution
prohibit the measurement of these changes during a single pass through the system.
When measured over an extended period of weeks, a change trend was observed, but a
mass balance calculation still remains impossible since an unknown, continuously
changing amount of tramp metals are introduced into the equation on an irregular basis
during normal processing.
The closest resemblance to a mass balance exercise one can conduct is an estimated
aluminum mass balance. The increase in aluminum contamination in the anodizing bath
during the Baseline Mode was 0.9 g/L. Normalized to the Ah of work completed during
that period, there was a 3.96 x 10~3 g/L rise in aluminum contamination for every 1,000
Ah. If that contamination rate is extended into the Operational Mode for the amount of
work done during that period, there should have been an aluminum contamination
increase of another 0.87 g/L in the anodizing bath. The bath, at 34,973 L the last day of
the test, should have generated an additional 30,480 grams of aluminum contamination.
If the actual analytical results for aluminum in the anodizing bath are totaled, the
RETEC system catholyte and the clarifier overflow, 23,431 grams of aluminum can be
accounted for (77 percent). (NOTE: aluminum and magnesium in the upstream and
downstream rinse tanks, as well as the raw chromic acid flakes was negligible, less than
0.85% of the aluminum generated during the test - see Table 8.) The missing 23 percent
of aluminum (7,049 grams, or 0.201 g/L in the anodizing bath) could be attributed to the
inherent limitation in precision of the analytical method, which was as high as 4 percent
for the DVI verification test. A variation of 4 percent translates to final aluminum
contamination reading of the anodizing bath of + 0.196 g/L (4.9 x .04), very close to the
missing 0.201 g/L. Metals solids can also precipitate out of solution from the catholyte.
A small amount of this granular solid, not accounted for in the analytical results, was
observed building up and settling to the bottom of the RETEC® reaction cell. Still more
is assumed to be at the bottom of the clarifier, but quantities were not ascertainable
18
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during the test period. Another explanation for the missing aluminum is the possible
formation of aluminum complexes in the anodizing bath, which the aluminum analytical
method does not measure. In the Electroplating Engineering Handbook by Lawrence J.
Durney [Ref 4], it is stated that dissolved aluminum can react with trivalent and
hexavalent chromium to form aluminum dichromate. This aluminum complex is not
detected by the aluminum analytical method used to measure the aluminum in the bath,
and could therefore account for the missing aluminum.
Sampling Week
0- Baseline
1- Baseline
2- Baseline
3- Baseline
4- Baseline
5- Baseline
6- Operational
7- Operational
8- Operational
9- Operational
10- Operational
11- Operational
Chromic Flake
Hexavalent
Chromium
(Colorimetric)
g/L
Upstream Rinse
/ Down Rinse
.043 / .0043
.0347. 0028
.0397. 0019
.0417. 0056
.053 / .0063
.0717. 0058
.048 / .0036
.0347. 0016
.0347. 0017
.083 7 .0046
Trivalent
Chromium
(Colorimetric)
g/L
Upstream Rinse
/ Down Rinse
< .00001 / .00052
< .00001 / .00056
< .00001 / .00035
< .00001 / .00069
<. 00001 /. 0004
< .00001 / .00099
<. 00001 /. 0005
< .00001 / .00046
<. 00001 /. 0007
< .00001 / .00042
Total
Chromium
(ICP-AES)
g/L
Upstream Rinse
/ Down Rinse
.041 7 .0049
.0317.0034
.0367.0021
.0387.0064
.047 7 .0071
.064 7 .0066
.0447.0041
.0317.002
.029 7 .0025
.0787.0055
Total
Aluminum
(ICP-AES)
g/L
Upstream Rinse
/ Down Rinse
.0033 /<. 0002
.0026 7 .0003
.0033 7 .0004
.00377.001
.0044 7 .0007
.00667.0014
.0045 7 .0007
.003 7 .0003
.0029 7 .0006
.0079 7 .0007
Total
Magnesium
(ICP-AES)
g/L
Upstream Rinse /
Down Rinse
.0157.016
.0157.015
.0157.015
.0157.015
.0157.015
.0157.015
.0147.015
.0157.015
.0157.015
.0167.016
Thanksgiving holiday - no samples collected this week.
.0517.0031
NA
< .00001 / .00029
NA
.0467.0036
480.0 (g/Kg)
.0049 7 .0005
0.15 (g/Kg)
.0157.016
1.2 (g/Kg)
NA = Not applicable
Table 8. Summary of Analytical Results (Rinse & Flake)
5.4 Hexavalent Chromium Air Monitoring Results
Baseline air monitoring results indicated an average process hexavalent chromium
emission of 0.1112 |J,g/m3. Personal exposure monitoring resulted in an average of
0.5199 ng/m3. Both readings are well within the Occupational Safety and Health
Administration (OSHA) Permissible Exposure Limit (PEL) of 100 |J,g/m3 and the
American Conference of Government Industrial Hygienists (ACGIH) Threshold Limit
Value(TLV)of50ng/m3.
19
-------
Operational air monitoring results showed an average process hexavalent chromium
emission of 1.3495 ng/m3. These readings are twelve times higher than the Baseline
results, however, they are still well below the OSHA and ACGIH limits. A certain
increase in process emissions was expected due to the aeration of the open-topped
RETEC clarifier that took place during the operational phase of the verification test. The
stationary air monitoring equipment collected samples from an elevated platform adjacent
to the RETEC clarifier.
Personal monitoring during the operational phase was performed, however, the worker
being monitored also performed maintenance on paint booth filters which contained dried
chromium containing paint flakes and dust. This activity contaminated the samples, so
the results were discarded.
Sample Location
RETEC Clarifier
Run No.
Run#l
Run #2
Run #3
Volume of Air
Sampled (m3)
1.89
1.96
1.96
Hexavalent Chromium
ug/sample
0.198
0.099
0.349
ug/m3
0.105
0.051
0.178
Table 9. Air Monitoring Results - Baseline Phase
Sample Location
RETEC Clarifier
Run No.
Run#l
Run #2
Run #3
Volume of Air
Sampled (m3)
1.88
1.88
2.05
Hexavalent Chromium
ug/sample
1.20
1.56
5.29
ug/m3
0.638
0.830
2.581
Table 10. Air Monitoring Results - Operational Phase
Operational air monitoring abnormalities withheld, the RETEC system exhibited a slight
increase in the overall hexavalent air emissions to the DVT facility. It is imperative to
realize that this increase only raised the DVI ambient air quality from 0.2% to 2.7% of
the ACGIH TLV. The results of the air monitoring are shown in Tables 9 and 10.
5.5 Energy Use
The primary energy requirements for operating the RETEC® system at DVI include
electricity for the system rectifier and liquid transfer pumps. Electricity is also used for
instrumentation and intermittent compressed air used for agitation; however, the energy
requirements for these are less significant and were not evaluated during this project.
RETEC® system rectifier electrical requirements (volts, amps and amp hours) were
recorded from gauges on the RETEC® system rectifier instrument panel each week. The
results are summarized in Table 11.
20
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Rectifier electricity use was calculated by multiplying total amp-hours by average system
voltage and dividing by 1,000 (3.11 x216,857/l,000) to get 675.9 kWh for the six week
Operational Mode of the verification test. This reduces to an average of 16.1 kWh/day.
Since the rectifier is left on at all times, the total annual consumption operating 365 days
per year is 5,876.5 kWh/yr.
Liquid transfer pump electricity use was calculated by multiplying the horsepower (HP)
of each system pump (1/25 and 1/16 HP) by .746 kW/HP-hr by the number of hours of
use. The result is 191.0 kWh/yr and 298.4 kWh/yr respectively, based on continuous use
(6,400 hrs/yr) of the pumps. Therefore the combined energy consumption for the liquid
transfer pumps is 489.4 kWh/yr, making the total electricity demands for the entire
RETEC® system 6,366 kWh/yr.
Test Mode/
Sample Date
Amperage
(amps)
Voltage
(VDC)
Amp-hours
(Ah)
Operational
10-19-00
10-26-00
11-02-00
11-09-00
11-16-00
11-23-00
11-30-00
Total
312
148
140
230
165
*
350
3.0
3.6
3.4
3.1
2.7
*
2.9
0
27,594
31,285
34,264
38,744
41,372
43,598
216,857
*No sampling taken during Thanksgiving; however, recording devices continued to measure and read data
-i®
Table 11. RETEC System Rectifier Electrical Requirements
5.6 Operating and Maintenance Labor Analysis
Operations and maintenance (O&M) labor requirements for the purification system were
observed during testing. Quarterly, the RETEC® cell is drained and cleaned. This
process was not observed during the verification test; however, interviews with
maintenance personnel and supervisors determined that it takes about 4 labor hours to
complete the cleaning and start-up procedure (16 hr/yr).
On a daily basis, operators periodically checked and recorded the anolyte and catholyte
flow rates, rectifier voltage/amperage and catholyte pH and made adjustments, when
necessary. At 5 minutes per shift, three shifts per day, five days per week (plus one shift
on Saturday), these daily tasks take approximately one hour and twenty minutes each
week to perform. On a 50-week/yr basis, operating checks take approximately 67 hrs/yr.
RETEC® system chemical additions are another maintenance labor requirement. Periodic
additions of chromic acid to the clarifier are necessary to keep the pH of the catholyte
under a pH of 2. Keeping the catholyte pH at this level prevents the precipitation of the
tramp metals and other contaminants as their respective hydroxides. Observation of the
maintenance personnel showed an average of 40 minutes per week dedicated to the
21
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preparation and addition of chromic acid to the catholyte. On a 50-wk/yr basis, chemical
additions take approximately 33 hrs/yr.
Typical equipment maintenance and parts replacement average about two hours per
®
month (24 hrs/yr). In summary, total O&M labor requirements for the RETEC system
average about 140 hrs/yr.
Other O&M labor associated with the chromic acid anodizing process, which is affected
by the operation of the purification unit, is the disposal and make-up of anodizing bath
chemistries. This process involves draining a pre-identified amount of the chromic acid
anodizing solution, and refilling the tank with fresh water and chemicals. Sometimes
DVI does a full bath dump (approximately 8,600 gallons), and sometimes they only do a
half bath dump (approximately 4,500 gallons). The amount of bath dumped is a decision
made by DVI management at the time of disposal. In either instance, the process takes
about five labor hours to complete. DVI performed two bath dumps in 1999, and two in
2000. Since the number of bath dumps was the same for each year, there were no
increases/decreases in O&M labor requirements based on bath dumps when RETEC is
turned on versus when it is turned off.
The number of make-up chromic acid additions when the RETEC® system was off in
1999 was 49, and when it was on in 2000, there were 46 additions, a decrease of 6
percent. In regards to Fumetrol 140 Mist Suppressant make-up additions, in 1999 there
were 31, and in 2000 there were 22, a decrease of 29 percent. At thirty minutes for a
chromic acid addition, and twenty minutes for a mist suppressant addition, this translates
to an annual savings of about 5 hours of O&M labor requirements. Net O&M labor
requirements related to the operation of the RETEC® system are 140 - 5 = 135 hrs/yr. No
additional O&M tasks were performed during the test period.
5.7 Chemical Use Analysis
From 3/20/99 to 1/3/00 (9.5 months), when the chromic acid anodizing purification unit
was off-line, DVI used the following chemicals:
• Anodizing tank new bath creation chromic acid flake: 3,300 Ibs.
• Anodizing tank new bath creation Fumetrol 140 Mist Suppressant: 16 gallons
• Anodizing tank make-up chromic acid flake: 5,710 Ibs.
• Anodizing tank make-up Fumetrol 140 Mist Suppressant: 16 gallons
This period saw 1,346,149 Ah of anodizing being completed. This normalizes an average
chemical consumption of 6.69 Ibs. of chromic acid flake and .0234 gallons of mist
suppressant per 1,000 Ah.
In 2000, from 1/3/00 to 9/6/00 (8 months), when the purification unit was on-line1, DVI
used the following chemicals:
• Anodizing tank new bath creation chromic acid flake: 3,300 Ibs.
• Anodizing tank new bath creation Fumetrol 140 Mist Suppressant: 18 gallons
1 The RETEC® system was off-line for a one month period (4/26/00 to 5/31/00) for an equipment design retrofit.
22
-------
• Anodizing tank make-up chromic acid flake: 5,370 Ibs.
• Anodizing tank make-up Fumetrol 140 Mist Suppressant: 13 gallons
• RETEC® system catholyte creation chromic acid flake: 85 Ibs.
• RETEC® system catholyte make-up chromic acid flake: 127 pounds
This period saw 1,360,124 Ah of anodizing being completed. This normalizes to an
average chemical consumption of 6.53 Ibs. of chromic acid flake and .0228 gallons of
mist suppressant per 1,000 Ah.
A comparison in chemical consumption results in a small decrease in chromic acid (0.16
Ibs. per 1,000 Ah) and mist suppressant (0.0006 gallons per 1,000 Ah) when the RETEC®
system is in operation. This translates to average annual chemical savings of 323 Ibs. of
chromic acid flake and 1.2 gallons of Fumetrol 140 Mist Suppressant.
5.8 Waste Generation Analysis
When the anodizing bath reaches its upper limit for aluminum contamination, it must be
disposed of, and a fresh anodizing bath must formulated. Sometimes DVI does a full
bath dump (approximately 8,600 gallons), and sometimes they only do a half bath dump
(approximately 4,500 gallons). The amount of bath dumped is a decision made by DVT
management at the time of disposal.
The purpose of the RETEC® system is to extend the anodizing bath life by removing the
tramp metal contaminants from the anodizing bath and concentrating them in the
catholyte, thus reducing the tramp metal contamination in the anodizing bath and
extending its life. When the catholyte reaches its upper limit for metals contamination,
and is no longer able to maintain the metals in solution, it must be sent for disposal (180
gallons) as well.
During the Baseline Mode, the RETEC® unit was turned off. The anodizing bath saw an
overall increase of 0.9 g/L of aluminum over this period. Normalized to the amount of
work measured in Ah during the Baseline Mode, this results in an average of 3.66 gallons
of chromic acid waste accumulation per 1,000 Ah.
In the Operational Mode, the RETEC® unit was on. The anodizing bath saw an overall
increase of 0.4 g/L of aluminum. Normalized to the amount of work measured in amp-
hours (Ah) for the Operational Mode, this results in an average of 1.68 gallons of
chromic acid waste accumulation per 1,000 Ah. The results are summarized in Table 12.
Date
09/14/00
10/19/00
10/19/00
11/30/00
Aluminum
Contamination
(g/L)
3.6
4.5
4.5
4.9
Anodizing
Completed
(Ah)
227,103
220,079
Total
Aluminum
Increase (g/L)
0.9
0.4
Waste
Generation
(gal/1,000 Ah)
3.66
1.68
Table 12. Results of Waste Generation Analysis
23
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The difference in aluminum accumulation between the two periods, 1.98 gallons per
1,000 Ah, is the apparent contamination reduction as a direct result of the RETEC®
system. At the total Ah of work performed during the Operational Mode, this translates
to 220 k Ah x 1.68 = 370 gallons of chromic acid waste. However, we have to account
for the added waste stream of the catholyte when the RETEC® system is in operation. In
2000, DVI had to dispose of the catholyte and clean the RETEC® unit four times, or once
per quarter. The Operational Mode of the verification test was just under 1.5 months, so
one-half (65 gallons) of a catholyte disposal/system cleaning will be accounted for h our
waste generation calculations. Therefore the RETEC® system generated 65 gallons of
additional chromic acid waste. Subtracting this from the waste disposal reduction of 370
gallons results in net savings of 305 gallons of chromic acid for the 1.5 month
Operational Mode of the verification test, or about 2,440 gallons of chromic acid waste
per year.
5.9 Cost Analysis
The capital cost of the RETEC® system was $35,230 (1993; includes $25,630 for the
electrolytic cell, pumps, stand and clarifier, $8,000 for the rectifier, and $1,600 for
installation costs).
Annual costs and savings associated with the chromic acid anodize solution purification
operation are shown in Table 13. The operating costs of the RETEC system are
$53,676. The operating costs of the anodizing bath prior to installation of the RETEC®
system were $61,964, resulting in net annual savings of $8,288. The simple payback
period is 4.2 years (capital cost/net annual savings).
Since some cost items are normalized to the workload as measured in amp-hours (Ah) for
each year, and the workload varies from year to year, the following table is based on a
fictitious 2,000,000 Ah year. (According to DVI operation logs, Tank #9, where the
RETEC® system is installed, saw 2,018,859 Ah in the year 2000).
24
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Item
Purification unit
O&M labor (see
section 5.5)
Chromic acid
anodizing tank
maintenance
O&M labor (see
section 5.5)
Chromic acid per
1,000 Ah (see
section 5.7)
Fumetrol 140 mist
suppressant per
1,000 Ah (see
section 5.7)
Electricity for
purification unit
(see section 5.4)
Waste disposal
fees per 1,000 Ah
(see section 5.8)
Total Costs
Prior to Installation of RETEC®
System
Units
0
35hrs
6.69 Ibs.
0.0234 gal.
0
3.66 gal.
Unit
Cost
$/unit
N/A
10.00
1.31
515
2.73
Costs/yr
(2M
Ahr/yr)
$
0
350
17,528
24,102
0
19,984
61,964
After Installation of RETEC®
System
Units
140 hrs.
30 hrs.
6.53 Ibs.
0.0228 gal.
6,366 kWh
1.98 gal.
Unit
Cost
$/unit
10.00
10.00
1.31
515
0.09
2.73
Costs/yr
(2M
Ahr/yr)
$
1,400
300
17,109
23,484
573
10,810
53,676
Table 13. Annual Costs/Savings
5.10 Project Responsibilities/Audits
Verification testing activities and sample analysis were performed according to section
6.0 of the Verification Test Plan [Ref. 2].
There were two verification test audits conducted during the verification period for this
technology. The first audit was an external EPA Technical Systems Audit (TSA)
conducted by subcontractor, John H. Nicklas of Science Applications International
Corporation on September 28, 2000. There were no Findings, two Observations and two
Additional Technical Comments. All corrective actions were completed as instructed in
the audit report issued by Mr. Nicklas.
The second audit conducted on this verification test was an internal CTC TSA conducted
by Mr. Clinton Twilley, CTC QA Manager, on November 9, 2000. Mr. Twilley
identified no Findings, three Observations and five Additional Technical Comments. All
corrective actions were complete as of the end of the verification test.
25
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6.0 REFERENCES
1. ELTECH International Corporation, "RETEC® CP Model 6 Chrome Purification
System Users Manual - Version 1.1. " March 1994.
2. Concurrent Technologies Corporation, "Environmental Technology Verification
Program for Metal Finishing Pollution Prevention Technologies Verification Test
Plan, Evaluation of USFilter RETEC® Separated Cell Purification of Chromic
Acid Anodize Bath Solution" September 13, 2000.
3. Concurrent Technologies Corporation, "Environmental Technology Verification
Program Metal Finishing Technologies Quality Management Plan" December 9,
1998.
4. Durney, Lawrence J. (ed). Electroplating Engineering Handbook, 4th Edition,
Chapman & Hall, London, UK, 1996.
5. Lenore S. Clesceri, Andrew D. Eaton, Arnold E. Greenberg (editors) Standard
Methods for the Examination of Water and Wastewater, 20th Edition, American
Public Health Association, and the Water Environment Federation, 1998.
6. Michael Murphy (ed). Metal Finishing 67th Guidebook and Directory Issue, Metal
Finishing Magazine, Volume 97, Number 1, January 1999.
26
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APPENDIX A
PRECISION CALCULATIONS
-------
PRECISION CALCULATIONS
Laboratory ID
L2002928-001
L2002928-001
L2002 928-001
L2002923-003
L2002923-005
N/A
N/A
N/A
N/A
L2003022-006
L2003022-006
L2003022-006
L2003022-005
N/A
N/A
L2003070-001
L2003070-001
L2003070-001
L2003089-005
N/A
N/A
L2003 163-005
L2003 163-005
L2003 163-005
L2003 163-005
N/A
N/A
L2003247-006
L2003247-006
L2003247-006
L2003247-005
N/A
N/A
L2003308-007
L2003308-007
L2003308-007
L2003308-007
N/A
N/A
N/A
N/A
N/A
N/A
L2003388-008
L2003388-008
L2003388-008
L2003388-001
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
L200348 1-008
L200348 1-008
CTCTD
Batch Sample
Batch Sample
Batch Sample
0914G-CC
0914H-CC
0914F-CT
0914F-CT
0914F-CTD
0914F-CT
0921H-M
0921H-M
0921H-M
0921H-CC
0921F-CT
0921F-CT
Batch Sample
Batch Sample
Batch Sample
0928H-CC
0928F-CT
0928F-CT
1005H-CC
1005H-CC
1005H-CC
1005H-CC
1005F-CT
1005F-CT
1012H-M
1012H-M
1012H-M
1012H-CC
1012F-CT
1012F-CT
1019H-CC
1019H-CC
1019H-CC
1019H-CC
1019A-CT
1019A-CT
1019A-CTD
1019A-CTD
1019B-CT
1019B-CT
1026H-M
1026H-M
1026H-M
1026H-CC
1026A-CT
1026A-CT
1026B-CT
1026B-CT
1026B-CTD
1026B-CTD
1026C-CT
1026C-CT
1102H-M
1102H-M
Parameter
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Aluminum
Chromium
Units
mg/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
g/L
g/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
g/L
g/L
g/L
g/L
g/L
g/L
mg/L
mg/L
Sample
Value
4.52
0.479
20.4
88.9
9.03
46.57
46.57
47.43
46.57
5.32
3.76
19.9
7.75
49.15
48.29
4.98
0.480
14.8
6.89
48.14
49.02
6.03
6.82
20.6
15.6
47.52
47.52
5.83
7.60
20.4
16.2
50.52
50.52
6.37
7.15
20.2
15.6
51.48
51.48
51.48
51.48
20.59
19.73
5.67
4.61
19.7
8.35
52.93
52.50
21.34
21.34
21.34
22.20
17.07
17.07
5.52
2.45
Duplicate
Value
4.46
0.475
20.3
89.6
9.10
50.02
46.57
49.15
46.57
5.26
3.75
19.8
7.70
47.43
47.43
4.95
0.480
14.8
7.00
48.14
49.02
5.96
6.75
20.5
15.8
47.52
47.52
5.85
7.57
20.4
16.3
50.52
50.52
6.37
7.30
20.6
15.6
51.48
51.48
51.05
51.48
20.59
19.73
5.67
4.62
19.8
8.34
52.07
52.07
21.34
21.34
21.34
21.34
17.07
17.07
5.42
2.50
RPD%
1
<1
<1
<1
<1
7
0
4
0
1
<1
<1
<1
4
2
<1
0
0
2
0
0
1
1
<1
1
0
0
<1
<1
0
<1
0
0
0
2
2
0
0
0
<1
0
0
0
0
<1
<1
<1
2
<1
0
0
0
4
0
0
2
2
RPD%
Limits
<30
<30
<30
<30
<30
<10
<10
<10
<10
<30
<30
<30
<30
<10
<10
<30
<30
<30
<30
<10
<10
<30
<30
<30
<30
<10
<10
<30
<30
<30
<30
<10
<10
<30
<30
<30
<30
<10
<10
<10
<10
<10
<10
<30
<30
<30
<30
<10
<10
<10
<10
<10
<10
<10
<10
<30
<30
RPDMet
Y/N
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
A-l
-------
Laboratory ID
L200348 1-008
L200348 1-007
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
L2003566-008
L2003566-008
L2003566-008
L2003566-007
N/A
N/A
N/A
N/A
N/A
N/A
L2003639-008
L2003639-008
L2003639-008
L2003639-007
N/A
N/A
N/A
N/A
N/A
N/A
L2003756-008
L2003756-008
L2003756-008
L2003756-007
N/A
N/A
N/A
N/A
N/A
N/A
crcro
1102H-M
1102H-CC
1102A-CT
1102A-CT
1102B-CT
1102B-CT
1102C-CT
1102C-CT
1102C-CTD
1102C-CTD
1102D-CT
1102D-CT
1109H-M
1109H-M
1109H-M
1109H-CC
1109A-CT
1109A-CT
1109B-CT
1109B-CT
1109C-CT
1109C-CT
1116H-M
1116H-M
1116H-M
1116H-CC
1116A-CT
1116A-CT
1116B-CT
1116B-CT
1116C-CT
1116C-CT
1130H-M
1130H-M
1130H-M
1130H-CC
1130A-CT
1130A-CT
1130B-CT
1130B-CT
1130C-CT
1130C-CT
Parameter
Magnesium
Hex chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Units
mg/L
mg/L
g/L
g/L
g/L
g/L
g/L
g/L
g/L
g/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
g/L
g/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
g/L
g/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
g/L
g/L
g/L
g/L
Sample
Value
19.3
6.68
52.93
52.93
23.05
23.05
23.05
22.20
22.20
22.20
16.22
16.22
5.25
2.81
19.6
4.18
53.78
53.78
36.71
36.71
25.61
25.61
5.69
5.96
21.2
9.41
53.78
54.83
41.83
43.54
25.61
26.46
5.32
4.03
20.6
7.68
53.29
53.29
51.60
51.60
45.68
46.52
Duplicate
Value
19.6
6.70
52.93
52.07
22.20
23.05
22.20
21.34
21.34
21.34
15.37
15.37
5.10
2.76
19.2
4.09
52.93
53.78
35.85
36.71
24.76
25.61
5.66
5.85
20.8
9.22
53.78
53.78
40.98
42.68
25.61
26.46
5.12
3.84
19.8
7.66
52.44
52.44
51.60
51.60
45.68
45.66
RPD%
2
<1
0
2
4
0
4
4
4
4
5
5
3
2
2
2
2
0
2
0
3
0
<1
2
2
2
0
2
2
2
0
0
4
4
4
<1
2
2
0
0
0
2
RPD%
Limits
<30
<30
<10
<10
<10
<10
<10
<10
<10
<10
<10
<10
<30
<30
<30
<30
<10
<10
<10
<10
<10
<10
<30
<30
<30
<30
<10
<10
<10
<10
<10
<10
<30
<30
<30
<30
<10
<10
<10
<10
<10
<10
RPDMet
Y/N
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
A-2
-------
APPENDIX B
ACCURACY CALCULATIONS
-------
ACCURACY CALCULATIONS
CTC
SAMPLED)
Batch Sample
Batch Sample
Batch Sample
0914G-CC
0914H-CC
0914F-CT
0914F-CT
0914F-CTD
0914F-CTD
0921H-M
0921H-M
0921H-M
0921H-CC
0921F-CT
0921F-CT
Batch Sample
Batch Sample
Batch Sample
0928H-CC
0928F-CT
0928F-CT
1005H-CC
1005H-CC
1005H-CC
1005H-CC
1005F-CT
1005F-CT
1012H-M
1012H-M
1012H-M
1012H-CC
1012F-CT
1012F-CT
1019H-CC
1019H-CC
1019H-CC
1019H-CC
1019A-CT
1019A-CT
1019A-CTD
1019A-CTD
1019B-CT
1019B-CT
1026H-M
1026H-M
1026H-M
1026H-CC
1026A-CT
1026A-CT
1026B-CT
1026B-CT
1026B-CTD
1026B-CTD
1026C-CT
1026C-CT
1102H-M
1102H-M
Parameter
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Aluminum
Chromium
Units
mg/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
g/L
g/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
g/L
g/L
g4
g/L
g/L
g/L
mg/L
mg/L
Sample
Value
<0.2
<0.01
15.6
43.3
4.31
48.1
46.7
48.6
46.7
0.32
3.36
15.4
2.83
48.1
48.1
0.2
0.01
9.87
1.86
48.1
49.02
1.07
6.29
15.5
5.59
47.5
47.52
0.73
7.07
15.3
6.26
50.5
50.5
1.41
6.76
15.5
5.77
51.5
51.48
51.5
51.48
20.6
19.73
0.71
4.14
14.9
3.57
52.7
52.21
21.3
21.34
21.3
22.3
17.1
17.07
0.31
2.04
Sample
+Spike Value
4.52
0.479
20.4
88.9
9.03
93.1
74.16
93.9
73.30
5.32
3.76
19.9
7.75
91.4
71.37
4.98
0.48
14.8
6.89
91.9
72.65
6.03
6.82
20.6
15.6
90.7
71.72
5.83
7.60
20.4
16.2
94.0
74.0
6.37
7.15
20.2
15.6
94.3
75.30
94.3
74.65
63.4
43.70
5.67
4.61
19.7
8.35
93.9
75.12
64.0
45.24
64.0
45.24
59.7
40.98
5.52
2.45
Spike
Value
5.00
0.500
5.00
50.0
5.00
43.0
24.0
43.0
24.0
5.00
0.500
5.0
5.0
43.0
24.0
5.00
0.500
5.0
5.0
43.0
24.0
5.00
0.500
5.0
10.0
43.0
24.0
5.00
0.500
5.0
10.0
43.0
24.0
5.00
0.500
5.0
10.0
43.0
24.0
43.0
24.0
43.0
24.0
5.00
0.500
5.0
5.0
43.0
24.0
43.0
24.0
43.0
24.0
43.0
24.0
5.00
0.500
Recovery %
90
96
96
91
94
104
114
105
110
100
80
90
98
100
97
100
96
99
101
101
98
99
106
102
100
100
100
102
106
102
99
101
97
99
78
94
98
99
99
99
96
99
99
99
94
96
96
95
95
99
99
99
95
99
99
104
82
Target %
Recovery
75-125
75-125
75-125
75-125
75-125
80-120
80-120
80-120
80-120
75-125
75-125
75-125
75-125
80-120
80-120
75-125
75-125
75-125
75-125
80-120
80-120
75-125
75-125
75-125
75-125
80-120
80-120
75-125
75-125
75-125
75-125
80-120
80-120
75-125
75-125
75-125
75-125
80-120
80-120
80-120
80-120
80-120
80-120
75-125
75-125
75-125
75-125
80-120
80-120
80-120
80-120
80-120
80-120
80-120
80-120
75-125
75-125
Accuracy
Met? Y/N
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
B-l
-------
CTCTD
1102H-M
1102H-CC
1102A-CT
1102A-CT
1102B-CT
1102B-CT
1102C-CT
1102C-CT
1102C-CTD
1102C-CTD
1102D-CT
1102D-CT
1109H-M
1109H-M
1109H-M
1109H-CC
1109A-CT
1109A-CT
1109B-CT
1109B-CT
1109C-CT
1109C-CT
1116H-M
1116H-M
1116H-M
1116H-CC
1116A-CT
1116A-CT
1116B-CT
1116B-CT
1116C-CT
1116C-CT
1130H-M
1130H-M
1130H-M
1130H-CC
1130A-CT
1130A-CT
1130B-CT
1130B-CT
1130C-CT
1130C-CT
Parameter
Magnesium
Hex chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Aluminum
Chromium
Magnesium
Hex chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Hex chrome
Total chrome
Units
mg/L
mg/L
g/L
g/L
g/L
g/L
g/L
g/L
g/L
g/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
g/L
g/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
g/L
g/L
g/L
g/L
mg/L
mg/L
mg/L
mg/L
g/L
g/L
g/L
g/L
g/L
g/L
Sample
Value
15.0
1.57
52.9
52.84
22.5
23.08
22.5
21.91
21.9
21.62
15.9
15.65
0.55
2.46
15.5
1.66
53.5
53.78
36.1
36.71
25.3
25.61
0.72
5.53
16.4
4.61
53.8
54.06
41.5
43.25
25.6
26.46
0.46
3.60
16.1
3.06
52.7
52.72
51.6
51.60
45.7
46.52
Sample
+Spike Value
19.3
6.68
96.0
75.98
64.8
46.10
64.0
44.39
64.0
44.39
58.8
38.42
5.25
2.81
19.6
4.18
96.4
77.66
78.5
60.61
68.2
48.6
5.69
5.96
21.2
9.41
95.5
76.83
83.6
67.44
66.5
50.37
5.32
4.03
20.6
7.68
94.7
75.2
93.8
75.28
87.9
69.36
Spike
Value
5.00
5.0
43.0
24.0
43.0
24.0
43.0
24.0
43.0
24.0
43.0
24.0
5.00
0.500
5.00
2.50
43.0
24.0
43.0
24.0
43.0
24.0
5.00
0.500
5.00
5.0
43.0
24.0
43.0
24.0
43.0
24.0
5.00
0.500
5.00
5.0
43.0
24.0
43.0
24.0
43.0
24.0
Recovery %
86
102
100
96
98
95
96
93
97
94
99
94
94
701
82
101
99
99
98
99
99
95
99
86
96
96
97
94
97
100
95
99
97
86
90
92
97
93
98
98
98
95
Target %
Recovery
75-125
75-125
80-120
80-120
80-120
80-120
80-120
80-120
80-120
80-120
80-120
80-120
75-125
75-125
75-125
75-125
80-120
80-120
80-120
80-120
80-120
80-120
75-125
75-125
75-125
75-125
80-120
80-120
80-120
80-120
80-120
80-120
75-125
75-125
75-125
75-125
80-120
80-120
80-120
80-120
80-120
80-120
RPDMet
Y/N
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
1 Accuracy results for this sample may be skewed due to relatively high concentration of sample analyte compared to the spike
concentration. The Laboratory Control Sample (LCS) was acceptable (91 percent), therefore, the data was approved. All
remaining accuracy checks for metals were within the goal of 75-125 percent.
B-2
-------
APPENDIX C
REPRESENTATIVENESS CALCULATIONS
-------
REPRESENTATIVENESS CALCULATIONS
CTCW
SAMPLE
0914F-M
0914F-MD
% Difference
0914F-CT
0914F-CTD
% Difference
0921 G-M
0921 G-MD
% Difference
0921 G-CC
0921G-CCD
% Difference
0928H-M
0928H-MD
% Difference
0928H-CC
0928H-CCD
% Difference
1019A-M
1019A-MD
% Difference
1019A-CT
1019A-CTD
% Difference
1026B-M
1026B-MD
% Difference
1026B-CT
1026B-CTD
% Difference
1102C-M
1102C-MD
% Difference
1102C-CT
1102C-CTD
% Difference
Aluminum
(EPA6010B)
3.6
4.2
-14.3
-
-
-
0.0026
0.0027
-3.7
-
-
-
0.0004
0.0004
0.0
-
-
-
4.5
4.3
4.8
-
-
-
2.0
2.0
0.0
-
-
-
2.6
2.3
11.5
-
-
-
Chromium
(EPA6010B)
49.0
53.0
-7.5
-
-
-
0.031
0.032
-3.1
-
-
-
0.0021
0.0021
0.0
-
-
-
46.0
45.0
2.2
-
-
-
20.0
19.0
5.0
-
-
-
20.0
18.0
10.0
-
-
-
Magnesium
(EPA6010B)
0.27
0.26
3.7
-
-
-
0.015
0.016
-6.2
-
-
-
0.015
0.015
0.0
-
-
-
0.32
0.27
16.0
-
-
-
0.12
0.12
0.0
-
-
-
0.13
0.12
7.7
-
-
-
Hex Chrome
(Titration)
-
-
-
48.0
48.6
-1.2
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
51.5
51.3
0.4
-
-
-
21.3
21.3
0.0
-
-
-
22.5
21.9
2.7
Tri
Chrome
(Titration)
-
-
-
<1.1
<1.1
0.0
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
<1.1
<1.1
0.0
-
-
-
<1.1
<1.1
0.0
-
-
-
<1.1
<1.1
0.0
Hex
Chrome
(SM-3500
CrD)
-
-
-
-
-
-
-
-
-
0.034
0.035
-2.9
-
-
-
0.0019
0.0018
5.3
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
Tri Chrome
(SM-3500
CrD)
-
-
-
-
-
-
-
-
-
ND
ND
0.0
-
-
-
0.00035
0.00036
-7.9
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
C-l
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