ALKALINE NONCYANIDE ZINC PLATING
WITH REUSE OF RECOVERED CHEMICALS
by
Jacqueline M. Peden
Hazardous Waste Research and Information Center
Champaign, Illinois 61820
Cooperative Agreement No. CR815829
Project Officer
Paul M. Randall
U.S. Environmental Protection Agency
Risk Reduction Engineering Laboratory
Cincinnati, Ohio 45268
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U S ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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NOTICE
The information in this document has been funded wholly or in part by the United
States Environmental Protection Agency (EPA) under Cooperative Agreement No. 815829,
This document has been subjected to the Agency's peer and administrative reviews, and it has
been approved for publication as an EPA document. This approval does not necessarily
signify that the contents reflect the views and policies of the EPA. Mention of trade names
or commercial products does not constitute endorsement or recommendation for use.
11
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FOREWORD
Today's rapidly developing and changing technologies and industrial products
frequently carry with them the increased generation of materials that, if improperly dealt with,
can threaten both public health and the environment. The U.S. Environmental Protection
Agency is charged by Congress with protecting the nation's land, air, and water resources.
Under a mandate of national environmental laws, the agency strives to formulate and
implement actions leading to a compatible balance between human activities and the ability of
natural systems to support and nurture life. These laws direct the EPA to perform research to
define our environmental problems, measure their impacts, and search for solutions.
The Risk Reduction Engineering Laboratory is responsible for planning, implementing,
and managing research, development, and demonstration programs to provide an authoritative,
defensible engineering basis to support the policies, programs, and regulations of the EPA
with respect to drinking water, wastewater, pesticides, toxic substances, solid and hazardous
wastes, and Superfund-related activities. This publication is one of the products of that
research. It provides a vital communication link between the researcher and the user
community.
This document presents the results of an experiment conducted to compare reductions
in the volume and toxieity of wastes that resulted from the change from a cyanide-based to an
alkaline noncyanide-based plating operation. This material substitution facilitated recovery
and reuse of both rinsewater and plating bath chemicals. An assessment of the economic
impact resulting from this modification is also provided.
E. Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
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ABSTRACT
A metal finishing process can create environmental problems because it uses chemicals
that are not only toxic but also resistant to degradation or decomposition. A study was
undertaken at a zinc electroplating operation to achieve zero discharge of wastewater and total
recycle of recovered precipitates. The first step in this project was to change an existing zinc
cyanide (CN) plating line to one that used an alkaline noncyanide (ANC) zinc bath. The
project then investigated a closed-loop system to treat plating rinsewater from the ANC zinc
plating line so the plating chemicals were recovered and the water purified. The goal was to
return both the recovered zinc hydroxide and the clean water to the plating line for continued
use. The system that was designed and installed, at P&H Plating Co., a Chicago area
operation, used precipitation by pH adjustment to remove the zinc from the rinsewater. The
precipitated zinc hydroxide was collected on filters, dewatered using a filter press, and stored
for reuse in the plating line as needed. Once filtered, the water was recirculated to the rinsing
portion of the plating line. The recovery/recycle system successfully purified the rinsewater
and facilitated the recycling of the cleaned water and the precipitated zinc hydroxide.
Eliminating cyanide from the plating process meant the line workers were dealing with a less
toxic plating bath, made compliance with regulations easier, and reduced treatment and
disposal costs for the company. The recycling of the recovered water and the zinc hydroxide
further reduced the costs for treatment and disposal. The replacement of this single CN line
with an ANC line resulted in an annual savings to P&H Plating of $14,000 from the
elimination of the need to pretreat the plating line rinsewater to oxidize cyanide. The
addition of the recovery/recycle system increased the company's savings to $62,000/year.
The reuse of 30% of the recovered zinc hydroxide and 70% of the treated rinsewater reduced
annual water usage and wastewater discharge by 841,911 gallons and reduced the amount of
sludge disposed annually by 14 cubic yards. The payback period for the recovery/recycle
system is slightly less than 18 months. Installation and use of this system for other ANC
plating operations would result in reductions in wastes and increased economic benefits
similar to those experienced by P&H Plating Co.
This report was submitted in partial fulfillment of Cooperative Agreement No.
CR815829 by the Hazardous Waste Research and Information Center under the sponsorship
of the U.S. Environmental Protection Agency. This report covers a period from January 1990
to December 1992. The work was completed as of December 18, 1992.
IV
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CONTENTS
Notice ii
Forward iii
Abstract * . iv
Figures vi
Tables ,., vii
Acknowledgements . ix
1. Introduction 1
2. Conclusions and Recommendations 4
3. Project Description 7
Industry Background 7
P&H Plating Co. Operation 8
The Plating Process ? 9
The CNT Recovery/Recycle (R/R) System 11
Bench Studies , 11
R/R System Description- , 13
R/R System Performance , t 13
Performance Summary 15
4. Results and Discussion 16
Plating Bath Conversion , 16
R/R System Evaluation 17
Zinc Hydroxide Quality 17
Zinc Hydroxide Recovery and Recovered Water Quality 22
Zinc Hydroxide and Recovered Water Reuse 22
Plating Quality Comparison 22
Toxicity Comparison 23
5. Economic Analysis 25
Capital Costs 25
Waste Produced and Disposal Costs 26
Operational Cost Comparisons . 27
Total System Comparisons 31
References 37
Appendices
A. Analytical Quality Assurance 40
B. Analytical Data 46
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FIGURES
NUMBER PAGE
1. Plating Lines with and without Closed Loop Recovery System „ 10
2. P&H Plating Alkaline Noncyanide Plating Line
With CNT Designed Recovery/Recycle System » 12
VI
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NUMBER
TABLES
PAGE
1. Comparison of Cost for Plating Bath Makeup Chemicals
for 1800 Gallon Solutions .......................................... 17
2. Comparison of Concentrations of Zinc, Iron, Calcium,
and Magnesium in Dried Zinc Hydroxide from the CNT System . . . ............ 18
3. Zinc and Iron Recovery from Initial Testing of CNT System . . . . . ............. 19
4. Concentration of Zinc in Water Samples Taken September 19, 1992 ........ . ---- 20
5. Percent Zinc Recovered During 3 Plating Runs .............. ............. 22
6. Breakdown of Costs for Design, Purchase, and Installation of
CNT Recovery/Recycle System ...... ................................. 25
7. Comparison of Weekly Chemical Maintenance Costs for CN and ANC Lines ...... 26
8. Comparison of Annual Operational Costs for CN Process, ANC Process
without R/R unit, and ANC Process with R/R unit at P&H Plating Co ............ 29
9. Assumptions for Economic Calculations .............. • ................. 31
10. Annual Operating Expenses for Zinc Cyanide Plating Line over 10 Years (Dollar Amount
Before Taxes and Depreciation) ..... ............................ ..... 32
11. Annual Operating Expenses for Alkaline-Noncyanide Plating Line over 10 Years (Dollar
Amount Before Taxes and Depreciation) ....................... • ......... 33
12. Annual Operating Expenses for Alkaline-Noncyanide Plating Line with Operational
Recovery/Recycle Unit ............................................ 35
13. Comparison of Economic Indices for the Alkaline Noncyanide Plating Process With and
Without the Recovery/Recycle system ............................ ...... 37
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APPENDIX B TABLES
NUMBER PAGE
B-l. Water Content of Zinc Hydroxide from CNT Recovery/Recycle System 46
B-2. Analysis of Dried Zinc Hydroxide Sludge Samples from P&H Plating Co 47
B-3. Carbon Analysis for Randomly Selected Zinc Hydroxide Sludges 48
B-4. Run Log for Analysis of Rinsewater Samples (Input) Taken During Initial Testing of
R/R System 49
B-5. Run Log for Analysis of Treated Water Samples (Output) Taken During Initial Testing
of R/R System 50
B-6. Contract Laboratory TOC Analysis of Rinsewater Samples Taken During Initial Testing
of R/R System 51
B-7. Run Log for Analysis of Zinc in Rinsewater Samples Taken September 12, 1992 and.
September 19, 1992 for the Final Evaluation of the R/R System 52
B-8. Run Log for Analysis of Zinc in Rinsewater Samples Taken September 7, 1992 and
October 10, 1992 for the Final Evaluation of the R/R System 53
Vlll
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ACKNOWLEDGEMENTS
The author would like to thank Cheryl Emrich and Jeff Pytlarz of P&H Plating Co. for their
participation in this project, particularly their persistence in making the system fully
operational. Engineers Henry Szadziewicz and Sam Mehta designed and installed the system
and performed the initial testing. HWRIC's laboratory staff, Aaron Weiss, Sarah Smothers,
Amy Hughes, Teresa Chow, and Jack Cochran, deserve special recognition for their work in.
analyzing difficult and complex samples. Thank you to the USEPA's peer reviewers, Paul
Randall, S. Garry Howell, Hugh Durham, and Teresa Harten and the HWRIC reviewers,
David Thomas, Gary Miller, Pam Tazik, Laura Mendicino, and Beth Simpson, whose
comments have made this a better report. Finally a special acknowledgement goes to Beth
Simpson for her help with the data analysis, to Angela Simon for incorporating the review
comments and preparing the camera-ready copy, and to Paul Randall for his assistance,
persistence, and patience.
IX
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SECTION 1
INTRODUCTION
The Waste Reduction Innovative Technology Evaluation (WRITE) Program was
implemented by the USEPA in 1989. In May of that year the Illinois Hazardous Waste
Research and Information Center (HWRIC) began its participation in the program with the
initiation of a three year project to evaluate a minimum of five pollution prevention
technologies currently used by Illinois industries. One of the industries targeted for
investigation was the electroplating industry. For the project, Alkaline Noncyanide Zinc
Plating with Reuse of Recovered Chemicals* HWRIC staff worked with contractors hired by
an electroplating company to evaluate the feasibility of using an innovative closed-loop
rinsewater treatment system to precipitate the plating chemicals for recovery and reuse and to
produce cleaned water that could be recirculated to the rinsing tanks and sprayers. The
system uses pH adjustment to precipitate zinc hydroxide from the rinsewater from an alkaline
noncyanide zinc plating process making the precipitate available for reuse hi the plating bath.
After precipitation, the treated rinsewater is of sufficiently high quality to be used again in. the
plating line.
This project represents a joint research effort of P&H Plating Co. (P&H) and the
Center for Neighborhood Technology (CNT), both of Chicago, Illinois; HWRIC, Illinois
Department of Energy and Natural Resources (ENR), Champaign, Illinois; and the U.S.
Environmental Protection Agency (EPA), Office of Research and Development, Cincinnati.,
OH.
The wastes generated from the electroplating processes are carefully regulated to
eliminate or at least reduce the threat that their disposal may pose to human health and the
environment. Treatment is almost certainly required before disposal. There are many
publications available that discuss the regulations and suggest technologies to meet the
regulatory requirements (Spearot 1993, USEPA 1987, USEPA 1985b, USEPA 1982).
Researchers have explored the feasibility of a centralized treatment facility for metal finishing
wastes (Comfort et al 1985). Others have examined technologies to reduce or recover and
reuse electroplating process wastes (Foecke 1986, USEPA 1985a, USEPA 1990, Walton and
Loos 1992, CDHS 1990, HWC 1990). Simple process changes such as slowing down the
withdrawal of the workpiece and increasing drainage time to reduce dragout can result in
significant reductions in the amount of plating bath chemicals found in or transferred to the
rinsewater wastes. Since the largest volumes of plating wastes are contaminated rinsewaters,
adoption of methods to reduce the volume and/or toxicity of these rinsewaters is desirable
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(USEPA 1990). Ideally, efforts should be made to recycle the rinsewater and to recover the
metals it contains so they too can be reused in the plating process or reclaimed for other uses.
Developing a closed-loop system to achieve this end would be beneficial both economically
and environmentally (Walton and Loos 1992). The design, installation, and testing of one
type of closed-loop system to reduce electroplating process wastes was the primary objective
of this study.
For this project, P&H Plating replaced one zinc cyanide-based barrel plating line with
one that used an alkaline noncyanide zinc plating bath. This new line was used to evaluate
the effectiveness of the recovery/recycle system designed by CNT engineers. The goal was to
recover zinc from the process rinsewater, recirculate the cleaned water, and approach zero
water discharge. Once precipitated, the zinc hydroxide was collected through filtration,
transferred to a filter press to remove residual water, then stored in a barrel until it was
needed to replenish the plating bath. The purified rinsewater was recycled through a closed-
loop system, developed and installed by CNT engineers, for reuse in both spray and
counterflow rinse tanks. Recovery of the zinc hydroxide and its reuse in the bath coupled
with the reuse of the cleaned rinsewater resulted in reduced operational and disposal costs.
HWRIC staff evaluated the effectiveness of the system in achieving waste reduction
by:
quantifying the effectiveness of the removal of zinc through precipitation by pH
adjustment, the basis of the recovery system;
determining the quality of the precipitate and the cleaned water that were recovered;
comparing the plating quality of the cyanide-based process to that achieved with the
alkaline noncyanide-based process which used both the recycled chemicals and the
treated rinsewater, and
• analyzing the costs associated with, the change in the process and the installation and
use of the recovery/recycle system.
Evaluation of the system continued for nearly two years. An initial 4 week analysis of
the recovery process indicated that it would indeed be effective in producing both zinc
hydroxide and water that could be reused in the plating line. After the system was in place
for three months, however, the plating quality had deteriorated and the system was bypassed
until the cause of the problem was determined. The persistence of the company and their
desire to employ recovery and recycling in then- facility resulted in resolution of the problem.
Once the problem was corrected, another period of evaluation of the recovery/recycle system
was undertaken to document the metal removal efficiencies and to determine the treated water
and precipitated zinc hydroxide quality. Data from these evaluations are included in Section
4 and Appendix B of this report. The original CNT recovery/recycle (R/R) system has been
modified slightly to accommodate larger volumes and flow rates than were anticipated in the
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original design discussions. The modified R/R system continues to be used at P&H Plating
on a single plating line. The new design will accommodate the use of the R/R system to
clean rinsewater from two lines. It is anticipated that this two line system could be
operational within two years.
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SECTION 2
CONCLUSIONS AND RECOMMENDATIONS
CONCLUSIONS
The CNT designed R/R system proved quite successful in meeting the project
objectives. By converting from a cyanide-based (CN) to an alkaline noncyanide-based (ANC)
plating bath, the company eliminated one step from the treatment cycle, i.e. the destruction of
cyanide which was no longer present in the wastewater from this plating line. The removal
of cyanide from the system also reduced the risk to employees by eliminating a highly toxic
substance from their work environment. The treatment of the wastewater proved so
successful that nearly all of the recovered water could be recycled as well as much of the
precipitated zinc hydroxide. As a result of installation of this recovery unit in the facility,
operational costs, including treatment and disposal costs, raw material purchases, and water
usage fees were reduced by approximately $62,000/year. The cost to design and install a R/R
system like the one in use at P&H Plating is recovered during 18 months of operations. The
reuse of 30% of the recovered zinc hydroxide and 70% of the treated rinsewater reduced
annual water usage and wastewater discharge by 841,911 gallons and reduced the amount of
sludge disposed annually by 14 cubic yards. Similar economic benefits are anticipated from
installation of this type of recovery unit hi other plating operations.
The goal of zero discharge and total recycle was not achieved for two reasons. The
rectifier that converts alternating current to the direct current required for the plating process
is tap water cooled (Cambria 1989). This cooling water flows into the counter flow rinsing
tanks on the plating line. As a result of this continuous addition of fresh water, only 70% of
the treated rinsewater is needed for the line. The company is currently exploring the
possibility of using the treated water in the rectifier cooling operation which if successful,
would meet the project goal of zero discharge.
Only 30% of the recovered zinc hydroxide is returned to the line for it is not a totally
suitable replacement for the zinc ingots traditionally used to replenish the plating bath zinc.
At present this precipitate can only be used on this test line as it is not suitable at all for the
CN lines; however, as the company converts to an all ANC zinc operation the precipitate can
be a raw material source for all of the lines. Additionally this precipitation process is
partially serving as a pretreatment step; the cost of the precipitation pretreatment is less than
would have been the cost of pretreating the cyanide containing rinsewaters. The compliance
criteria that need to be met by the final treatment are only those for zinc, since there is no
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longer cyanide in this rinsewater. The maximum discharge levels for metals are generally
easier to achieve than those for cyanide, resulting in reduced treatment costs and fewer
compliance problems.
All of the precipitate produced is passed through the filter press which greatly reduces
its volume. The unused portion is stored for later use or disposed as a hazardous waste.
While it would be possible to petition to delist this waste, the amount being produced is less
than 5% of the total metal waste that the company produces and must routinely dispose.
Since much of the other metal waste was from cyanide-based lines and probably contained
residual amounts of cyanide, even after treatment, it was disposed as a hazardous waste. It is
currently more economically advantageous to simply add the zinc hydroxide to that waste and
dispose of it as hazardous rather than separating it, storing it, and attempting to have it
delisted (Anderson 1993). As the company converts all of its plating lines from cyanide-
based to noncyanide-based it will experience even greater economic and environmental
benefits. This change will eliminate the need for cyanide destruction in the company's
treatment operations. One major compliance problem will also be eliminated as will potential
health risks associated with cyanide exposure.
Although the goals of the project were not totally achieved, the use of this system has
proven to be economically beneficial to the company. The change to an alkaline noncyanide
bath has reduced the toxicity of the plating line and its resulting wastes. .The water and
chemical recycling made possible by the CNT designed R/R system has reduced operational
costs. Direct results of this recycling effort are reduced water usage, fewer raw material
purchases, lower treatment costs, and smaller volumes of waste needing disposal. This
system is simple and functions well. It is in use at P&H Plating today and its use in other
similar electroplating operations would result in economic benefits comparable to those
experienced by P&H.
RECOMMElSnOATIONS
Cyanide-based plating baths are still the most widely used type of bath, despite the
costs of pretreatment, treatment, and disposal. The tightening of discharge limits and the ban
on land disposal of cyanide containing wastes have made their replacement by less toxic,
more easily treated bath chemicals desirable. Cyanide-based systems are well defined,
making analysis and control of the concentration of plating bath chemicals relatively simple
processes. Extensive pretreatment or cleaning of the parts to be plated is not required. The
final products are generally of very high quality with uniform, hard, bright, corrosion resistant
plated deposits. This process, however, requires the use of highly toxic chemicals and
produces equally toxic wastes that are difficult and expensive to treat and dispose (Cushnie
1985).
While the toxicity and waste treatment problems inherent in zinc cyanide plating can
be substantially reduced by changing to the use of noncyanide plating bath chemicals, there
are significant obstacles to changing the plating process. In terms of product quality, the
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alkaline noncyanide zinc plating finish is not as lustrous nor is its color the same as that
produced by a cyanide zinc process. This can be a serious problem since customers
frequently equate quality with appearance and find the noncyanide finish unacceptable
aesthetically. Also, the alkaline noncyanide plating process requires the plating surface to be
much cleaner than the surface being plated by a cyanide-based process. Many shops are
unable to provide this more stringent parts cleaning (Kansupada 1985).
Despite these problems, alkaline noncyanide plating produces a hard, corrosion
resistant finish which at least equals and may exceed that produced by the cyanide zinc
process. The potential reduction in toxicity and operating costs that result from making this
plating process change warrants increased efforts to overcome customer concerns about the
luster and color of the finish and encourage their acceptance of the alkaline noncyanide zinc
plated products (Kansupada 1985).
HWRIC and USEPA agree that there are many pollution prevention opportunities for
the electroplating industry left to explore (USEPA 1992). HWRIC continues to work with
electroplaters to develop and document other waste reduction technologies. Documented case
studies of process modifications and technology evaluations that lead to source reduction are
available but more should be prepared (Kohl et al 1985, Kirsch and Loobey 1991,
NCDNRCD 1985, USEPA 1993, Lindsey and Peden 1994). Distribution of this information to
the appropriate audience can be achieved with the assistance of trade groups for the
electroplating industry. Continued association with these industry organizations is essential to
identify new pollution prevention options and to promote adoption of those that have
succeeded. This continued interaction can only benefit all parties involved* Economic benefit
could be substantial to the companies willing to work toward source reduction. The
environmental benefits that could result from the reduction in toxicity and volume of this
industry's wastes would be significant and would be reason enough to continue to support the
research that will bring about those reductions.
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SECTION 3
PROJECT DESCRIPTION
In this section, general information about the electroplating industry and P&H Plating
Co.'s operation is provided. Also discussed briefly is the bench scale study that was used to
develop the CNT recovery/recycle (R/R) system and the information that was used to
formally evaluate its performance. A detailed description of the CNT R/R unit and how it
operates are provided.
INDUSTRY BACKGROUND
Electroplating is a process used to coat metal or plastic objects with one or more
metals. This is achieved by submersing an object into a solution of dissolved metal ions and
passing an electrical current through the solutions. The result is the deposition of the metal
onto the surface of the object. The most commonly used plating metals are: brass, bronze;,
cadmium, chromium, copper, lead, nickel, tin, and zinc. The plating solution or bath may
contain metal salts, alkaline compounds, and additives designed to reduce irregularities in the
plating finish and increase the brightness of the finished surface (EMPE, Inc. 1986).
Waste reduction in the electroplating industry is important to achieve for several
reasons. The metal finishing process can create several environmental problems for it uses
chemicals that are not only toxic but also resistant to degradation or decomposition (UNEP
1989). The electroplating wastewater pollutants of greatest concern are toxic metals, cyanide,
toxic organics, and conventional pollutants such as suspended solids, oil, and grease (USEPA
1985).
Many opportunities exist in electroplating operations to achieve waste reduction. The
design and operation of the system used to move the parts through the plating line will
determine how much plating solution is dragged out into the wastewater. Simple steps such
as submerging the plating barrel half way, which will generally still ensure complete
submersion of the parts being plated; increasing drain time; and installing sloped drain boards
can mean significant differences in the amount of dragout. Other options include recovering
bath chemicals, cleaning and recycling rinsewater, using less toxic chemicals when possible,
and using technologies such as ion exchange to clean and maintain plating baths (USEPA
1990, USEPA 1985a). Adoption of these types of process modifications are generally not
only environmentally advantageous, but also result in economic benefits from their
implementation.
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Federal and state regulations have been developed to eliminate or reduce these
pollutants in the environment by setting limits on the amdunts of toxic plating line
constituents that can be discharged (USEPA 1985b). The current federal standard for the
maximum discharge level of zinc is <4.5 mg Zn/L for daily discharge and <2.6 mg Zn/L for a
4 day average discharge, and for total cyanide it is <1.9 mg/L/day and <1.0 mg/L for a 4 day
average (Martin 1992). Local compliance standards may be even more restrictive. For
example, P&H must comply with the discharge standards for the Metropolitan Water
Reclamation District of Greater Chicago (MWRDGC 1991) which are 0.10 mg CN'/L and 1.0
mg Zn/L for discharge to waters and 5.0 mg CN"/L and 15.0 mg Zn/L for discharge to
sewage systems. The cost to the electroplating industry to comply with these regulations can
be considerable. These costs include not only those for disposal of the waste stream but also
the expense of pretreatment to reduce the volume and/or toxicity before disposal is even
possible.
Cyanide is a particularly difficult contaminant to treat. It readily combines with iron
to form very stable complexes which may not be completely precipitated by standard
treatment methods. The treatment process may not always be functioning efficiently resulting
in incomplete cyanide removal from the company's effluent (Martin 1992). Enforcement
efforts on both the state and federal levels are well coordinated. Inspector training and
information sharing are on the rise in local communities, the states, and the federal
government. The penalty for violators will certainly include monetary fines, sometimes in the
millions of dollars, and may also include a prison sentence (Krukowski 1992). It therefore
becomes essential for electroplaters to develop an integrated approach to waste management
that meets compliance standards and includes waste reduction as a vital component.
The Harris Directory (1992) lists 5,200 companies under the Standard Industrial
Classification (SIC) Code 3471, plating and polishing, in the United States with 331 residing
in Illinois. A review of the County Business Patterns for 1989-1990 (Bureau of the Census
1993) indicates that there are 174 plating operations (SIC 3471) located in Cook County. In
these Chicago facilities, one can find a wide variety of metals being plated on an assortment
of surfaces. The plating of zinc on steel parts is common to many Chicago plating
companies. While the majority of these companies use cyanide-based plating baths,
operations employing noncyanide plating baths with zinc hydroxide and zinc chloride as the
plating bath chemical are growing in number (Kansupada 1985). The parts that are plated
range from nuts, bolts, and other common hardware items to automobile parts and metal
furniture. Zinc plating is designed to be both functional (preventing corrosion) and decorative
(providing an attractive appearance).
P&H PLATING CO. OPERATION
HWRIC researchers worked with P&H Plating Co., a large Chicago plating job-shop
that operates 16 hours a day, 6 days a week and employs 100. It uses barrels, hoists, and
racks to move parts through the plating operations. For this study a barrel line that plates
zinc on small steel parts such as washers, nuts, bolts, and hinges was used. Although the
project concentrated on zinc plating, the shop is capable of and does plate nickel, brass,
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copper, arid cadmium on a variety of surfaces. The facility contains a waste treatment area
which receives effluent at an average rate of 150 gallons per minute (gpm). Pretreatment of
the wastewater is required for effluent from the cyanide and chromate plating lines. The
cyanide wastewaters are treated with hypochlorite to destroy cyanide complexes and comply
with current standards for discharge of metals and cyanides into the sewer. The pretreatect
wastewaters are combined and the metals are removed principally by precipitation. The
precipitate is collected as sludge and disposed according to current regulations. The treated
wastewater is tested and discharged, if all of the regulatory criteria are met, and returned for
additional treatment if they are not >
In this project, two changes were made to one of the zinc barrel plating lines. First,
the plating solution was changed from a zinc cyanide (CN) bath to an alkaline noncyanide
(ANC) zinc bath. Although there are examples of successful plating operations replacing CN
bams with ANC baths (FM 1992, CDHS 1990) there was still concern at P&H that the plate
achieved with the ANC process would not meet their customers' satisfaction. By changing to
the ANC process, the company could explore the possibility of implementing a waste
reduction technology to recover the plating line wastes. Once the change to ANC actually
occurred, a linsewater purification system was installed to recover both water and zinc
hydroxide for reuse hi the plating line. The objectives of this project were to evaluate these
changes by examining the reduction in toxicity and volume of the waste and assessing the
effectiveness of the recovery of zinc hydroxide from the waste water. The feasibility of using
the treated water and the precipitated zinc hydroxide in the plating lines was also explored!
and the economic benefits resulting from the use of the CNT R/R system'determined.
THE PLATING PROCESS
In the original operation of the plating line (which is the current operation of the 5
plating lines that were not modified for this project), workpieces were placed in the barrel and
subjected to several precleaning steps before plating. The plating tank for the modified line is
divided into 8 stations each capable of holding one barrel. The barrels with the workpieces
(in this study generally small steel items such as washers and nuts) inside were dipped into
the plating tank for approximately 25 minutes (time and current will vary somewhat by job).
From the plating tank, the barrel and its contents moved to the spray rinse tank where 4
nozzles sprayed water into the barrel for 20 seconds at a rate of 7 gallons per minute. The
barrel then moved on to two additional counterflow rinse tanks where it was submerged for
approximately 2 minutes. The rinse spray and overflow from the counterflow tanks were
collected, pretreated to oxidize the cyanide (Cushnie 1985) then sent to the waste treatment
area where they were treated to comply with state and local effluent requirements before
being discharged. Figure la is a very general schematic of the plating and rinsing operation.
The change that was evaluated for this project is represented in Figure Ib. The modification
was to direct the rinse water through a closed loop recovery system and return the treated
water to the counterflow rinse tanks instead of simply sending the effluent stream to the waste
area for treatment and disposal.
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Workpiece
Counter Flow Rinse tanks
A. Typical Plating Line Schematic
Workpiece Plating bath
Waste Treatment
B. Plating Line with Closed Loop Recovery System
Figure 1. Plating lines with and without Closed Loop Recovery System
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THE CNT RECOVERY/RECYCLE (R/R) SYSTEM
The principles involved in the design of the CNT R/R system were relatively simple
and similar to the standard wastewater treatment of flocculation to remove metals prior to
disposal of water and sludge wastes. Once the change was made from the cyanide plating
bath to one that used noncyanide compounds, the zinc that was "dragged out" into the
rinsewater could be easily precipitated as zinc hydroxide by simply adjusting the pH of the
solution. Most of the precipitated zinc hydroxide settled to the bottom of a clarifying tank.
From there it was collected and returned to the plating bath. Water from the clarifying tank
was pumped through filters to remove and collect suspended zinc hydroxide. The filtered
water was returned to a holding tank for reuse in the rinsing process and the zinc hydroxide
collected on the filters was returned to the plating bath.
Figure 2 is a schematic of the R/R system that was finally installed and is currently in
use at P&H. Ideally, 100% of the zinc in the rinsewater would be recovered and returned to
the plating bath. Additionally, all rinsewater would be recycled. The projected result would
be substantial savings for the company in plating chemicals and water from this rinsewater
purification that both recovers and reuses as well as treats.
Bench Studies
Two bench scale studies were needed to determine the optimum pH for complete
precipitation and the correct pore size for maximum retention of the zinc hydroxide. To
determine the optimum pH for the zinc hydroxide precipitation, the pH of aliquots of a known
concentration of zinc hydroxide solution were adjusted at intervals of 0.2 pH units from a pH
of 9.5 to pH 11.1. Approximately 50 minutes (the residence time of the rinsewater in the
continuous stirred reactor (CSR) and clarifying tank based on the size of the tanks and system
flow rate) after the pH adjustment, the solutions were filtered. The percent of zinc
precipitated and the zinc concentration of the filtrate were determined. These tests indicated
that a pH between 10 and 10.5 was ideal and a pH monitor and a controller were purchased
and placed on the CSR to determine the pH of the rinsewater and to adjust and maintain it
between pH 10 and 10.5.
The original standard that was used to determine whether the water was suitable for
return to the rinse tank was that its zinc content should be less than the minimum discharge
level for zinc allowed by the Water Reclamation District of Greater Chicago which is <4.5
mg/L daily and <2.6 mg/L for a 4 day average. During the bench studies, however, it was
found that the recovery system could successfully remove the zinc to concentrations of <0.5
mg/L. This concentration (0.5 mg/L) became the new standard used in the bench study in
both the determination of the optimum pH range for maximum precipitation and the proper
pore size selection for complete removal of the precipitate.
The system design employed a dual filtration unit. A pump, placed approximately 2
feet above the bottom of the clarifying tank, was used to draw the rinse water through the
11
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dual filter unit. A series of tests using filters varying in pore size by 2 micron were made to
determine the proper pore size to use to best accommodate the projected flow rate of 10
gallons per minute (gpm) and meet the <0.5 mg/L of zinc standard. As a result of these tests
the unit consists of two consecutive filters with the first having a pore size of 12-15 microns
to remove the coarser particles and the second, a pore size of 3-4 microns to remove the finer
fraction of the precipitate.
R/R System Description
In the plating process at P&H there is the usual parts pretreatment or cleaning,
followed by plating spray rinsing, and finally, submerging into two counterflow rinse tanks.
Although cleaning requirements for ANC plating are generally more stringent than those for
CN plating, no change was required to the pretreatment portion of the line at P&H. The
company had already installed a very stringent cleaning component to their plating lines to
ensure good parts cleaning and, presumably, better plate quality. This cleaning was more
than was needed on the CN lines and quite acceptable for the new ANC line. The CNT B[/R
system was plumbed from the spray rinse tank into which the counter flow tanks ultimately
overflowed. The rinsewater flows from the rinse tank (CFSR) into the reactor tank where the
pH is measured and automatically adjusted.
This pH monitoring and control tank is a continuous flow stirred reactor. It is
designed to allow adequate mixing to stimulate precipitation. Compressed air from an air
sparger at the bottom of the tank is used for mixing in the R/R system. The flow rate
through the reactor is set at lOgpm. The next step is to allow settling of the precipitated zinc
hydroxide. This is accomplished in a flat bottomed clarifying tank. To facilitate the settling
process, the tank is baffled. A recirculating pump pulls water from the clarifying tank
through the dual filtering system to remove suspended hydroxide. The treated water is then
either sent to the storage tank for reuse or to the waste treatment area for additional treatment
prior to discharge. The settled precipitate is removed through a port near the bottom of the
clarifying tank and combined with the precipitate collected on the filters. This composited
hydroxide is put through a filter press to remove as much water as possible. The water that
is removed is returned to the precipitation reactor and the de-watered hydroxide is analyzed
and stored for future use or disposed if not needed. Figure 2 shows the system components
and the way the water and solids flow through the system.
R/R System Performance
The initial testing of the system took place over 4 weeks. The design engineer ran, the
system from 8-16 hours a day during that period. The initial design differed somewhat from
that depicted in Figure 2 and it was this 4 week test period that exposed the design flaws and
allowed the time to implement the changes that made the system perform as desired.
The early design flaws were the result of planning a system for a rack operation, but
ultimately implementing it on a barrel line. The original concept was proposed for use by
13
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another plating company. The bench studies and subsequent system components selection
were based, on calculations of dragout that would be expected from a rack plating operation.
Financial problems forced the first industrial participant to withdraw. P&H agreed to
participate, but was considering the change to the alkaline noncyanide process for one of their
barrel lines. The original system design could use components P&H already had available
which would mean minimal additional costs to P&H. This first system had many mechanical
problems. It was modified to include: separate precipitation and settling tanks, stirring
capabilities for the precipitation tank, baffles in the settling tank, a valve in the settling tank
to facilitate removal of the settled precipitate, a valve in the water recycling line and the
water storage tanks to bleed off excess water to the treatment area, and a filter press to
dewater the hydroxide.
These changes were needed for several reasons. The dragout from the barrel was
much greater than that from the rack which meant more precipitate to be filtered and frequent
clogging of the filters ultimately resulting in considerable downtime. Sparging in the
precipitation tank hastened the precipitation process, so a minimal amount of zinc hydroxide
remained suspended in the water. The sparging coupled with the installation of the settling
tank and the valve to remove the settled material, dramatically reduced the filter clogging and
the system downtime. Inclusion of a filter press to dewater the recovered hydroxide reduced
the volume of the precipitated solids, making the precipitate a more suitable additive to the
plating bath and reducing the cost of disposal of the material that couldn't be used. The
water recovered from the press operation could then be returned to the R/R system and
ultimately recycled. These component changes did not eliminate all of the problems, but
solved the major ones so that the system has remained in use for almost 3 years without
needing further modification. Additionally, downtime for extensive system maintenance has
been eliminated. A schedule has been established for routine checks of the mechanical
components and the filters are replaced and cleaned every few weeks as needed. (The
maintenance schedule is dependent on the number and types of jobs that are run on the line.)
Another major concern resulting from the change to an ANC-based system and the use
of recovered materials was that of maintaining the plating quality. There has been a problem
with customer satisfaction with the parts plated by this new process. Quality is typically
linked to appearance. Because the plating luster is not quite as bright as with a cyanide-based
process, the customer assumes that the corrosion resistance and other protective features for
which the plate is applied have been adversely affected. Salt spray corrosion tests were
performed to ensure protection was not compromised, but customers are not always easily
convinced. This is a problem that is difficult to resolve. When changes in product
appearance are equated with negative changes in product quality, one tactic to overcome this
customer dissatisfaction has been to highlight the environmental and economic benefits
resulting from reduced plating costs for the company due to the new ease in meeting
compliance limits which also translate into reduced costs to the customer. These are very real
problems for platers considering the switch from cyanide to less toxic materials and the
potential loss of customers may prove to be too large of an uncertainty for some platers to
risk by changing to safer plating process alternatives.
14
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While the initial testing of the system showed promise, it was not without problems.
It was through the persistence of the facility chemists that success was finally achieved.
After several months of returning the precipitated zinc hydroxide to the plating bath, a
noticeable and unacceptable change in plating quality was observed. HWRIC staff were
concerned that the probable cause of the problem was the buildup of organic brighteners and
their byproducts that were being collected with the zinc hydroxide precipitate and returned to
the plating bath. Analysis by HWRIC's chemist, however, found no measurable organic
carbon in either the treated water or sludge.
During the system shutdown to resolve the plating quality problems recovered zinc
hydroxide was not used. The bath was adjusted as usual with new materials. Testing by the
analytical laboratory normally used by P&H discovered that the problem actually was caused
by excessive iron levels in the zinc anode balls used in the bath. These were replaced and the
CNT R/R system was again put to full use. The system continues to operate and function as
designed.
Although in this instance brightener buildup did not play a role in plating quality
deterioration, it has the potential to affect the plate. Monitoring of the chemicals used in the
bath is important. The recycling efforts may mean different additives are needed to ensure a
high quality product The willingness of the chemical supplier to assist the plating operation
with this monitoring is critical to the implementation of new systems that employ a recycling
option.
PERFORMANCE SUMMARY
This project began as a short term evaluation of a new technology to reduce
electroplating wastes. Had it remained that, important information would have been lost and
the evaluation would have been basically correct but flawed. Since the resolution of the
plating quality problem, the CNT R/R system has been in continuous use at P&H.
Maintenance of the system is minimal, consisting of proper care of mechanical parts and
periodic replacement and cleaning of the filters. Zinc hydroxide is removed from the rinse
streams with an efficiency averaging 84%. The amount of precipitate recycled to the system
varies depending largely on the number of jobs that will require use of that line. On average,
the company recycles 30% of the zinc it recovers. The quality of the treated rinsewater is
generally acceptable for recycling and/or discharge. Essentially, the system works and is in
use providing both environmental and economic benefits to P&H.
15
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SECTION 4
RESULTS AND DISCUSSION
The use of the CNT R/R system has indeed been beneficial to the company, its
employees, and the environment. Comparisons of plating wastes and other operational factors
prior to and after installing the system clearly show the benefits. The comparisons examined:
product quality, toxicity/safety differences, amounts and types of wastes produced, quality of
the products of the R/R system, and use of the recovered materials.
P&H routinely collects and analyzes samples to assess the bath and the plating quality.
While these analyses are vital to the successful operation of the plating lines, they did not
really provide the information that was needed to evaluate the recovery/recycle capabilities of
the CNT system. HWRIC staff used four full day sampling opportunities to obtain the
samples used for the CNT R/R system assessment. The sampling took place over a month
and occurred approximately 1 year after the system had been installed. During the first 6
months after installation, there were several problems, including previously discussed design
flaws, that had to be resolved. By the time the HWRIC sampling effort took place, all of the
system problems had been corrected and the unit had been in successful, routine operation for
6 months. The data from the analyses of samples taken from the early testing and those
taken during this one month effort were used to quantify the effects of the change in the
plating operation.
PLATING BATH CONVERSION
If a company were to start up a new plating line, it would begin the process by
determining the cost of the bath chemicals for each alternative - the cyanide (CN) or the
alkaline noncyanide (ANC) zinc plating solutions. This assessment would show that the total
costs of make-up chemicals for each plating solution option were essentially the same -
$1,771 for the CN bath and $1,860 for the ANC bath. These costs are broken down by
cost/bath chemical in Table 1. Labor and water used in the bath preparations would be
essentially identical, so those costs were not included in the calculations.
P&H, however, was not starting a new line but replacing an existing line. Since the
company was still operating other CN zinc lines, the plating bath could be stored and used as
needed in those other lines. Had this storage option not been available, the 1,800 gallon CN
zinc bath that was being replaced would have to be treated and then disposed at a cost of
$16-20/gallon. Additionally, the ANC system does not function properly in the presence of
16
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cyanide. Since the equipment in the line had previously handled CN zinc it had to be
thoroughly washed. No attempt was made to quantify the amount of water used in this
rinsing process. It was simply treated as wastewater from the line and piped to the waste
treatment area for processing and disposal. This water was not considered in the economic
evaluation presented in Section 5.
TABLE 1. COMPARISON OF COST FOR PLATING BATH MAKEUP CHEMICALS FOR
1800 GALLON SOLUTIONS
Zinc Cyanide Bath
Chemical Cost $
Alkaline Noncyanide Zinc Bath
Chemical Cost $
NaCN
NaOH
Zn
Brightener
Totals
404
249
1064
54
1771
NaOH
Zn(OH)2
Brightener
560
1100
200
1860
R/R SYSTEM EVALUATION
To evaluate the effectiveness of the system, the amount and quality of zinc recovered
from the rinsewater were determined. Additionally the quality of the recovered water was
determined. Finally, the amount of the recovered materials that were recycled was calculated.
The monetary value of the recycled chemicals and the water were calculated and used to
determine the time required to recover the costs associated with the bath chemical substitution
and the development, construction, and implementation of the CNT R/R system. Data used to
assess recovery and quality are summarized in this section. The raw data are available in
Appendix B.
Zinc Hydroxide Quality
Grab samples were taken from the filters and the bottom of the clarifying tank and
analyzed for metal content Metal concentrations were determined using atomic absorption
spectroscopy following the sample preparation and analyses methods described in SW-846
(USEPA 1986) in accordance with the quality assurance plan for the project The company
routinely analyzes metal sludge samples prior to disposal. The contract laboratory that it uses
for these determinations performed the analyses of the zinc hydroxide precipitate during
CNT's testing of the R/R system. Since the most likely contaminants in the precipitate were
oxides of iron from the parts being plated and calcium and magnesium from the tap water
used throughout the system, concentrations of these metals were determined in addition to the
concentration of zinc. The contract laboratory analyzed 32 samples for total solids content to
17
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assess the amount of water in the zinc hydroxide from the R/R system. Water content was
consistent ranging from 86% to 93% and averaging 88% (see Table B-l). The samples were
dried to a constant weight (a change of <0.2mg) then analyzed for zinc, iron, calcium, and
magnesium at HWRIC's laboratory. Table 2 summarizes the data from these analyses. The
standard deviations are included to indicate the variation that existed within the sample set.
The data used to generate Table 2 are found in Appendix B (Table B-2).
TABLE 2 COMPARISON OF CONCENTRATIONS OF ZINC, IRON, CALCIUM, AND MAGNESIUM IN DRIED
ZINC HYDROXIDE FROM TH E CNT SYSTEM
Analyzing N
Laboratory
HWRIC Lab 32
Zinc
Mean %
64.4
SD
8.02
Iron
Mean %
0.93
SD
0.78
Calcium
Mean %
3.27
SD
2.43
Magnesium
Mean %
1.61
SD
1.20
"N=Number of samples analyzed
The analysis of the recovered zinc hydroxide led to the following actions. Although
iron, calcium, and magnesium are present in the precipitate, the concentrations of these
materials were found to be at levels that should not effect plating quality; therefore, analysis
of these three contaminants was not performed on subsequent samples. Zinc concentrations
alone were used to assess quality and recovery. The percentage of zinc in pure zinc
hydroxide is 66% and the mean found in the dried R/R system precipitate is 64%, so the
precipitate is very suitable for recycling in the plating bath. The major problem with the R/R
system precipitate was the amount of water it contained. The company preferred not to use
heat to dry the precipitate and chose instead to purchase a filter press for dewatering. The
press was added to the recovery unit and effectively dried the precipitate. Because the
precipitate was then stored prior to being returned to the plating bath, additional drying
through evaporation to the air took place. Water from the pressing operation was recycled
through the R/R system.
A subset of these 32 samples was used to investigate the cause of the deterioration in
plating quality that occurred approximately 6 months after the system became operational.
Six samples were selected at random and analyzed for TOC following the method prescribed
in SW-846 (USEPA 1986). It was suspected that the plating quality problem resulted from a
buildup of brightener being carried into the bath on the recovered precipitate. Appreciable
levels of TOCs (>1%) (Table B-3) were found in only one of the six samples analyzed.
Other analytical anomalies were found in this sample, such as reduced levels of zinc (~45%)
and high levels of iron (>5%) (Table B-2), which raised questions about its integrity. During
the time the analyses were being performed, P&H's chemist discovered that the zinc ingots
used in the plating process were not the purity required by the system. These were replaced
and plating quality improved immediately, so no further investigation of the problem was
undertaken. Since organic carbon was not present on these samples taken when there were
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problems, it was assumed this would be the case for the other samples and TOC was
eliminated as one of the test parameters.
Zinc Hydroxide Recovery and Recovered Water Quality
The CNT engineer had originally planned to use the amount of zinc measured in the
rinsewater and the amount of precipitate produced by the R/R system to calculate the percent
removal of zinc. This assumed a constant flow through the system at a known flow rate or
an accurate measurement of the volume of water passed through the system in a run.
Unfortunately, the flow through the system is variable and could not be used to calculate the
volume of water passing through the system. There were also no devices installed in the
system to measure the rinsewater volume, so another means of calculating zinc recovery was
used. The concentration of zinc in the rinsewater before entering the R/R system was
determined and compared to the concentration of zinc in the water leaving the system. The
difference was divided by the amount of zinc originally measured in the rinsewater,
multiplied by 100% and reported as %Zn removed.
During the initial period of testing by CNT, two types of samples were taken, the
rinsewater and the zinc hydroxide precipitate. The analysis of the precipitate samples was
discussed in the previous section on recovered metal quality. Like the precipitate samples,
the rinsewater samples were grab samples. They were taken from a sampling port in the
piping to the R/R system (input samples) and from the overflow valve on the purified water
holding tank (output samples). These rinsewater samples were analyzed by HWRIC's
laboratory for zinc and iron. Four samples were randomly selected and analyzed for total
organic carbon CTOC) as well. The zinc concentrations were to be used in the calculation of
the %Zn recovered. The analyses for iron were to determine the levels of possible
contaminants. Although the presence of contaminants such as iron and organic carbon
compounds would not affect plating quality since the cleaned water would be recycled to the
rising portion of the plating line, it was useful to obtain some indication of their
concentrations to assess whether the cleaned water could be used for other purposes such as
replenishing the plating baths. Table 3 summarizes the analyses for zinc and iron for this set
of samples (see Tables B-4 and B-5 for raw data). TOC values were at the method detection
limit (1.0 mg/L) (Table B-6) and are not included on the table. Since the amount of iron and
TOC were so small, they were not analyzed in the samples taken later in the evaluation.
TABLE 3. ZINC AND IRON RECOVERY FROM INITIAL TESTING OF CNT SYSTEM
Analyte N* Input Mean (SD) mg/L Output Mean (SD) mg/L % Recovered
Zinc
Iron
16
16
190 (±61)
0.48 (± .18)
19 (+23)
0.38 (+ .38)
90
21
*N=Number of samples analyzed
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Theoretically, measuring the concentration of the metal in the rinsewater being put
into the R/R system and then measuring tHIs concentration of the metal in the water that has
passed through the system and is about to be recycled should allow you to calculate the
percent of zinc removed. In practice this technique is not totally accurate. The difficulty is
how do you compare what went in to what came out? How long do you wait from the time
you start up the system and take the input sample to grab the output sample? Again, because
there were no devices in the system to measure flow, this period could not be calculated.
Additional factors also play a role here.
When the plating bath is not in use, the R/R system is turned off. Whatever solution
remains in the lines and tanks of the system sits until it is again activated. Because of the
need to cool the rectifier there is a period after the plating operation stops when clean water
is being added to the rinse tanks. There is another period at the start of a plating run where
the dragout has just begun and the metal levels have not built up as they will later when
several barrels have been, through the plating and rinsing steps. What this leads to is a
cycling of metal concentrations in the input and output waters. HWRIC laboratory staff tried
to account for these factors in the. sampling effort made towards the end of the project. Input
samples were taken after the first barrel of parts was rinsed and the output sample was taken
approximately half an hour later. Table 4 is the data from the analyses of the samples taken
on September 19, 1992. The input samples are rinsewater from the ANC line before it
entered the R/R system and the output samples are water that had passed through the system
and was about to be recycled. These data are a good example of the changes in the zinc
concentrations as the plating operation progressed from start-up, through the plating of parts,
to shutdown of the line.
TABLE 4. CONCENTRATION OF ZINC IN WATER SAMPLES TAKEN SEPTEMBER 19, 1992
• Input mg/L Output mg/L
250 10
180 21
290 32
"270 69
It is interesting to note that the zinc levels in the output sample (which had passed
through the recovery process) increased with time. This was normal for the system. Since
the levels are fine for rinsewater reuse, no attempt was made to determine why this occurred.
It is probably because the precipitate remains in the clarifying tank from the start of the run
through the end of the run. Precipitate removal takes place once the line is shut down. The
concentrations of zinc in the water could easily show this level of increase simply as a result
of the stoichiometry of the precipitation reaction and the amount of precipitate present hi the
tank at the end of the run. While the water being recycled may not have always been suitable
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to discharge, it was acceptable for reuse in both the rinsing portion of the plating line and in
the plating bath itself where zinc was present in concentrations >50%.
To determine zinc recovery, four sets of samples were taken. These samples were
grab samples taken from sampling ports in the input and output lines of the R/R system.
Each sample set consisted of four input and four output samples. The first input sample was
taken after the first barrel with parts had passed through the plating line. The approximate
time of the plating operation for the day was determined and the second, third, and fourth
input samples were taken at quarterly intervals. A fairly typical sequence would be: start up,
first sample at one and one half hours, second sample at three and one half hours, third
sample at five and one half hours, and final input sample at seven and one half hours. Output
samples were all taken at about one half hour after each input sample. The percentage of
zinc recovered by the system was calculated by determining the concentration of zinc in the
input sample, subtracting the concentration of zinc in the output sample collected ~one half
hour later, dividing that difference by the input concentration and multiplying by 100%.
Using this method, the %Zn recovered ranged from 55% to 99%. The large range for the
percent recovery is a factor of the cyclical nature of the system input and output that was just
discussed. Because of this variability, it was decided to use each data set as a whole
calculating % recovery as the [(mean input)-(mean output)] •*• mean input x 100% rather than
calculating the recovery between individual input/output pairs. This approach should.more
accurately portray the % recovery for each plating run.
Blank problems were encountered during the analysis of one sample set which could
not be resolved, so only three data sets were used to calculate % recovery of zinc. Table 5
presents the percentage of zinc that was recovered by the R/R system and also provides mean
input and output zinc concentrations used for the calculation. The standard deviation about
each mean is provided to indicate the variability of the zinc concentrations within the set.
The actual data sets used are found in Tables B-7 and B-8. When the data are evaluated in
this way, the %Zn recovery ranges from 75% to 89% and averages 84%. Although 100%
recovery of zinc from the rinsewater was not achieved, the amount that was recovered is
reasonable. Additionally while not all of the samples of the outflow had measured zinc
concentrations low enough to discharge, the average output levels for each set of samples was
within the discharge limits or very close to them. Since these means would more closely
approximate the composite sample that would be tested for metal concentrations before
further treatment or discharge, these data suggest that the system could generally generate
recovered water that could be discharged without additional treatment.
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TABLE 5. PERCENT ZINC RECOVERED DURING 3 PLATING RUNS
Run Number Zinc Concentration' Zinc
Recovered %
Input Mean (SD) mg/L Output Mean (SD) mg/L
1
2
3
68 {+ 59) ,—
248 (± 48)
38 (± 15)
17 (+20)
33 (± 26)
4{± 2)
75
87
89
* Means were calculated from 4 samples
Zinc Hydroxide and Recovered Water Reuse
As stated previously, the precipitated zinc hydroxide is collected from the settling
tanks and scraped off the filters, then placed in a filter press for dewatering. The zinc
hydroxide is then stored until needed in the plating line. During this storage additional drying
of the precipitate occurs as the result of evaporation of precipitate moisture to the air. All of
the precipitate obtained from the R/R system could eventually be recycled into the plating
operation. The company estimates 30% of the zinc hydroxide recovered from the ANC line
is recycled.
Recovered water is also collected until needed. Because of the cooling system for the
rinsing baths, fresh water is being added to the rinsing tanks. As a result of this input, all of
the recovered water was not needed. The water storage system was designed so that overflow
from the storage tank was directed to the wastewater treatment unit for the facility where it
was pooled with other wastewaters from the plant, treated, and discharged. The company
estimates 70% of the water recovered is reused.
PLATING QUALITY COMPARISON
While the reasons for plating are sometimes purely ornamental, more frequently the
plate provides protection. Finishes may be bright or dull and it may not always be possible
to achieve the desired luster with the ANC system, although advances in the last decade have
provided less toxic bath alternatives that produce parts more like the bright, shiny objects that
result from a cyanide-based operation (Cushnie 1985). Ultimately, whether the plate is
satisfactory or not is up to the customer, but there are two standard tests that can be
performed to check quality. The first is to measure thickness. The desired thickness of the
plate is generally determined by the use that will be made of the item being plated. There are
industry standards for specific items as well as those required to meet customer specification.
While the ANC process may not always be the most suitable to the customer needs, the
current generation of ANC baths offer better coverage than and color comparable to CN
systems (Kansupada 1985). To test the ability of each process to meet the thickness
standards metal washers were plated on both lines and thickness measured. Both systems
22
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produced acceptable levels of thickness. The CN plated parts measured 0.0004 inches for the
zinc plate and the ANC plated parts, 0.0005 inches of zinc.
To assess the corrosion resistance imparted to the object as the result of the zinc
plating, these washers were subjected to salt spray testing, following ASTM method B 117
(ASTM 1990). The test objects are suspended in a chamber and sprayed with a salt solution
and then checked at designated intervals for signs of corrosion. Washers plated by the CN
process showed white (zinc oxide) corrosion after 10 hours and rust after 500 hours of
exposure. The washers from the ANC line also show white corrosion after 10 hours but the
rust did not appear until 700 hours exposure. This difference is most likely due to the thicker
zinc plate on the ANC plated parts, and is probably not significant.
A second salt spray test had similar results. Three sets of washers (50 in each set)
were subjected to salt spray testing. The three sets were washers plated on a CN zinc line,
washers from the ANC line before any chemical recycling took place, and washers from the
ANC line using recycled chemicals and water. In each set approximately 6% (2-4 washers)
of the parts showed white corrosion after 10 hours with rust appearing between 700 and 1,000
hours, generally on 50% or more of the pieces. The corrosion protection from each of the
three plating lines was essentially the same. The variation among the three test sets of
washers was 2% (1/50 parts), Le. the number of washers showing signs of corrosion hi each
set was the same at almost every time recorded. Additionally, the protective quality of the
plate is deemed acceptable when parts are subjected to the salt spray for periods longer than
24 hours before rusting begins. Using this criterion both the CN and ANC baths provided
acceptable corrosion protection.
TOXICITY COMPARISON
Had there been no economic benefit from the change to ANC plating the reduction in
health and environmental risk resulting from the elimination of cyanide from the process
would have been sufficient to warrant its adoption. CN zinc plating does require extensive
treatment before disposal and uses chemicals hazardous to human health. Chemical
substitution to achieve source reduction, as was done for this project, not only reduced
process costs but also the company's liability because of the reduction in the toxicity of the
chemicals being handled and disposed (CDHS 1990). *
The exposure of shop workers to toxic chemicals presents the most serious health and
safety problems for the electroplating industry. Although no occupational illness has been
documented for electroplating operators, they are routinely exposed to hazardous substances
which are known to cause serious health problems. Cyanide is generally considered the most
potentially dangerous of the electroplating chemicals. It is highly toxic when adsorbed
through the skin or ingested, and may be fatal if absorbed in quantities as low as 50-100 nag.
Despite this fact, deaths are rare, generally occurring from inhalation of hydrogen cyanide gas
that results from acidification of CN plating baths that have spilled on the shop floor or into
23
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floor drains. Because cyanide is so toxic, its use in most shops is carefully monitored and
employees are trained to use it properly. Training is essential to worker safety in all plating
operations. Combining employee education with substitution of less toxic chemicals may
provide the least costly and most productive control of workplace hazards. Replacing cyanide
plating solutions with noncyanide baths is strongly recommended (Winter and Facciolo 1985).
Not only is there risk to the health of the workers in the facility, but there are
potentially greater risks to the environment resulting from the discharge of cyanide to
waterways or the land. Slow bleeding of very dilute cyanide wastewaters and even spent
plating baths into the sewer system was not an unusual practice in the 1970s when
environmental regulations were just starting to address toxic chemicals and their release to the
environment. The slow discharge diluted the cyanide so it was not dangerous. But even at
low concentrations, cyanide may be toxic to fish and other inhabitants of the waterways into
which the waste stream was discharged after processing at the local publicly owned water
treatment works. A dramatic example of what could happen from this sort of practice
occurred in 1989 in Chicago. A spent plating bath (4,000 gallons) containing cyanide was
being slowly discharged into the sewer. This illegal discharge probably would have gone
unnoticed had it occurred over two weeks as intended, but someone did not adjust the
discharge valve properly and the entire spent bath solution was discharged overnight. The
result was a major (20,000) fish kill in the Chicago River, the closing of the city's northwest
side treatment facility, and fines and imprisonment for the company and its owner
(Krukowski 1992). Removal of cyanide from the process does not totally eliminate the health
or environmental risk associated with plating operations. Their wastes are still quite toxic.
But this chemical substitution does reduce the risk and some potential liability, for it removes
a potentially lethal constituent from both the process and the waste.
A somewhat quantitative evaluation of toxicity using a computer program that rates
waste streams as non-toxic, toxic, or highly toxic was originally proposed. This analysis was
not possible because cyanide in the waste stream causes it to be classified as lethal at all
concentrations. The program is aborted and no rating can be obtained to compare to the
"toxic" rating given to the ANC wastes. Modifications to that program are being considered
to enable this kind of comparison to be made on cyanide containing samples in the future.
24
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SECTION 5
ECONOMIC ANALYSIS
CAPITAL COSTS
The total costs for the equipment, design, and labor associated with the R/R system
was $51,822. Table 6 provides a breakdown of the actual costs. Costs for the make-up
materials for the CN and ANC plating baths were $1,771 and $1,860 respectively (see Table
1 for breakdown by chemical). Depletion of plating bath chemicals results from the
deposition of .the metal on the part and dragout of the plating solution into the rinsing tanks.
Weekly costs associated with maintaining the plating baths are $446.50 for the CN bath and
$424.50 for the ANC bath. The breakdown of these weekly maintenance costs is provided in
Table 7. As mentioned earlier, the bath quality of the CN plating line is not as critical to
achieving good plating quality as it is in the ANC plating operation; therefore, fewer analyses
of the CN bath are required. Additionally, the analytical parameters of the two plating baths
differ. Analysis for cyanide content in the ANC bath is not necessary, thus the cost for 5
analyses/week for the ANC bath is less than 2.5 times that of the 2 analyses/week for the CN
bath.
TABLE 6. BREAKDOWN OF COSTS FOR DESIGN, PURCHASE, AND INSTALLATION OF
CNT RECOVERY/RECYCLE SYSTEM .
Initial Investment Cost$
Equipment (includes pumps, tanks, pipes, valves,
pH controller, and filter press) 14910
Design and Start-up Labor
CNT 15612
P&H 13300
Bath Conversion Labor (P&H) 8000
Disposal of CN Bath 36000
Total 87822
25
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TABLE 7. COMPARISON OF WEEKLY CHEMICAL MAINTENANCE COSTS FOR
GN AND ANC LINES
CN Bath
ANC Bath
Component
Cost$
Component
Cost$
NaCN
NaOH
Zn Anodes
Brightener
Analysis (2x / week)
Total
34.00
22.50
120.00
220.00
50.00
446.50
NaOH
Zn Anodes
Brightener
Analysis (5x / week)
Total
105.00
120.00
129.50
70.00
424.50
WASTE PRODUCED AND DISPOSAL COSTS
The primary wastes from any plating operation are the rinsewater, spent or dirty
plating baths that must be discarded, metal sludges from routine removal of plating bath
contaminants (which may be done either electrically or mechanically), and unacceptable
plated products. For the CN and the ANC plating lines, we assumed the amount of
unacceptable products to be the same. Total replacement of the plating baths is not normally
needed. Plating baths are maintained by routine cleaning and addition of depleted chemicals
as needed. The cleaning operations for both the CN and ANC baths result in a mixed metal
sludge that must be disposed (following pretreatment to oxidize cyanide for the sludge from
the CN operation). The amount of mixed metal sludge resulting from the cleaning of each of
these plating systems is essentially the same, so it is not considered as a variable in the
operating costs calculation. The annual cost for the cyanide oxidation for this mixed metal
sludge is included in the cost comparison of the two systems.
The rinsewater from the CN and ANC lines also have different treatment needs and
associated costs. For the CN line, the wastewater is first sent to the cyanide destruct unit of
the facilities wastewater treatment area. Once the cyanide is oxidized, the wastewater is
mixed with wastewater from the rest of the facility's plating operation and metals are
precipitated as mixed sludges and disposed. For the ANC line, there is no cyanide to treat, so
the wastewater goes directly to the R/R system where it is precipitated as reasonably pure
zinc hydroxide. This precipitate can be used to replenish the ANC bath being studied and
any others that might exist in the facility. It might also be sold for other uses. The R/R
system keeps the ANC line waste segregated thus facilitating recycling options. At present
P&H Plating Co. is recycling only a portion of the recovered materials. Since there are no
longer any CN zinc lines at P&H Plating, the potential uses for the R/R system precipitate
have increased and the company is now considering using the excess from that line to
replenish other ANC lines.
26
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Because this test plating line is one of many generating the waste the plant produces,
and because there is an efficient waste treatment unit operating in the facility, the economic
benefits of the recycling effort made possible by the installation of the R/R system are not
obvious when examining the annual waste disposal costs for the company. This would not be
the case if the R/R system were being used throughout the facility on all appropriate lines or
even on all ANC lines. With additional waste stream segregation leading to recovery of
useable products and their recycling even more, substantial savings would be realized.
Treatment and disposal costs at P&H for a single zinc plating line typically amount to
>$100,000/year. The annual disposal costs for metal sludges during the period the R/R
system was being tested, were slightly above $52,000. Approximately 50% of this sludge
resulted from zinc plating operations at the company thus zinc disposal costs were $26,000.
This amount includes transportation costs. The unused zinc hydroxide precipitate being
disposed accounts for 5% of the total sludge being produced at P&H and costs $2,600
annually for disposal. Annual treatment costs for the wastewater from the CN line during the
project were $14,000 for cyanide oxidation and $69,000 for metal removal and collection
.resulting in a total treatment cost of $83,000. These costs include chemicals but not the labor
required for wastewater treatment. Labor is assumed to be comparable to that needed for the
operation of the recovery system (10 hours/week). These treatment costs are reduced by the
removal of cyanide from the process. Even greater reductions in these costs are achieved
with the use of the R/R system which has an annual operational costs of $10,900 ($7,500 for
labor, $400 for chemicals, $1,000 for utilities, and $2,000 for parts).
OPERATIONAL COST COMPARISONS
Because the company does not have electrical and water metering on each line, it is
difficult to assess the differences in these areas that have resulted from the installation of the
system. We will assume that the annual output from each line (calculated as the number of
parts plated) is the same and look at the different: power and water needs of the two
operations required to produce that output. There are some general differences in water and
power consumption between the CN and ANC systems that can be compared and used hi the
calculation of operational costs.
The rectifier for the CN line is air cooled, but the one for the ANC system is water
cooled. The air cooling is accomplished by a fan which will use electricity that is estimated
to increase the power needs of the line <5% per plating run. The water cooled unit does not
require this added electrical need. Furthermore, the water used to cool the rectifier is cycled
into the rinsing tanks and constantly replenishes the rinsewater. This steady source of new
water means only 70% of the recovered rinsewater is recycled.
Although the operating voltage/amperage for the plating line varies with the items
being plated and the type of plate required, for comparable runs the CN line routinely
operates at lower voltage and amperage. The duration for a similar run on each line also
27
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varies for the plating efficiency is better when using the ANC process meaning that a thicker
plate can be achieved in a shorter period of time. While there may be problems associated
with obtaining plating thicknesses >0.0008 inches with the ANC process, the parts plated at
P&H with both the CN and ANC lines require thicknesses <0.0005 inches which is easily
achieved. The efficiency of the ANC plating process is particularly good in the 0.0003 -
0.0005 inch thickness range, which is the range required for the parts generally plated at
P&H. Although the ANC consumes more power while it is operating, it is operated for a
shorter period to achieve a plate of similar thickness and quality to that produced by the CN
line. At a rate of $0.10/kilowatt hour (the cost to Commonwealth Edison customers in
Chicago) the additional power consumption for the CN operation required for rectifier cooling
would be a very small portion of the overall operating costs for the plating line. Because the
power usage is not directly measured and will be very similar for the two systems, power
consumption is not used for the calculations in the economic assessment that follows.
Labor costs for the operation of the plating portion of the lines are assumed to be the
same; however, there are new costs associated with the operation of the R/R system. There
are weekly labor costs of ~$150 (10 hours at $15.QO/hour). Sulfuric acid is used to adjust the
pH and promote the precipitation process at an annual cost of $400. Finally, annual power
costs to keep the recovery system in operation are ~$1000 (estimated by P&H).
While the reduction in risks may be sufficient to justify the change from CN to ANC,
the economic benefits that can result from such a change most certainly encourage its
adoption. When a R/R system is installed on the ANC line, the economic benefits become
too significant to dismiss. A comparison of the costs for the first year's operation of the
ANC line, and then to the ANC line with the R/R unit to the annual costs of the CN
operation is summarized in Table 8. Most of these costs have already been discussed.
Although there will be down times for all of the plating lines because of maintenance and the
number of jobs the company is processing, it was suggested by the company that calculations
be made for eight hours a day, five days a week, and 50 weeks per year. This should provide
a reasonable estimate of the annual work load for each plating line as the lines frequently
operate during two eight hour shifts, six days a week for 52 weeks.
Bath component costs were listed in Table 1 (p. 17). Weekly maintenance costs for
each plating bath were provided in Table 7 (p. 26). For the CN and ANC lines the annual
costs were derived by simply multiplying these weekly costs by 50 weeks. For the ANC with
R/R line, 30% of the zinc hydroxide was used to replenish the zinc in the plating bath. To
account for this recycling effort, the weekly costs of the zinc portion of the maintenance costs
was reduced by 30% making the weekly costs $388.50 instead of $424.50 for an annual cost
of $19,425 rather than $21,225.
28
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TABLE 8. COMPARISON OF ANNUAL OPERATIONAL COSTS FOR CN PROCESS,
ANC PROCESS WITHOUT R/R UNIT, AND ANC PROCESS WITH R/R UNIT AT P&H PLATING CO.
Process Operation
Bath makeup
Bath maintenance
CN Costs ($)
1771
22325
ANC Costs ($)
1860
21225
ANC + R/R* Costs ($)
1860
19425
Water usage
(Flow rate 10gpm)
1.Use@$7.56/7480g 1213 1213 364
2. Sewering @ $5.59/7480g 897 897 269
Wastewater treatment
1. Cyanide oxidation 14000 0 0
2. Metal precipitation 69000 69000 20700
3. Labor 7500 7500 2250
Sludge disposal 2600 2600 1820
Total 119306 104295 46688
* Assumes 70% water and 30% zinc hydroxide recycled
For the city of Chicago, the water usage charge includes costs for the amount of water
actually used and the amount sewered. The flow into the recovery unit is 10 gallons per
minute (gpm) and the same flow rate was assumed for the CN line and the ANC line without
the recovery unit. The total number of gallons used on each plating line is then calculated as:
Total gallons used = 10 gallons/minute x 60 minutes/hour x
8 hours/day x 5 days/week x 50 weeks/year.
The total water needed by the CN and ACN lines using this calculation is 1,200,000
gallons/year. Because of the recycling effort on the ANC with the R/R system, only 30% of
that amount (360,000 gallons) of fresh water is required The amounts sewered for each line
will be the same as water needed. The rates provided by the City of Chicago Water
Operations group are based on $13.15/1,000 ft3 (1,000 ft5 = 7480 gallons) broken down as
indicated in Table 8. Total water costs for the CN and ANC lines where no recycling takes
place are the same, $2,110. If the R/R system is used, 70% of the water can be recycled,
thus reducing both the amount needed and the amount sewered for a total cost of $633 which
saves the company $1477 in annual water charges per plating line.
Wastewater treatment costs are reduced by the change from CN to ANC and then are
even further reduced by installing the R/R system. To determine treatment costs, P&H
Plating Co. personnel used the total costs of the all treatment steps divided by the percentage
29
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of the waste stream coming from each line. These costs include chemicals and power usage.
Treatment for the CN line requires pretreatment (cyanide oxidation) followed by metal
precipitation and collection for a total cost of $83,000. Once cyanide is no longer used in the
operation, the only treatment needed is metal precipitation and collection which saves the
company $14,000, the costs that would have been needed for cyanide oxidation. Adding the
R/R system to the ANC line results in even greater savings. Because 70% of the wastewater
is passed through the R/R system and reused, only 30% is sent to the facility treatment unit.
Although this water should be essentially metal free, it is treated as if zinc were present;
however, the volume has been reduced by 70% resulting in a 70% reduction in treatment
costs for ANC with R/R, making those costs $20,700.
Labor is presented as a separate item because it must be calculated for both the facility
treatment unit and the R/R system. The R/R system requires 10 hours of labor per week with
an average rate of $15.00. Because the volume of wastes are the same and the types of
process used to treat and recover/recycle the wastes are so similar, 10 hours a week at
$15.00/hour to process the CN and ANC waste waters in the facility treatment unit are
assumed. Table 8 does not include the R/R system operational costs in its comparison.
While labor for CN and ANC wastewater processing would indeed be the same, adding the
R/R water recycle to the ANC line would reduce the labor cost because the volume of water
was reduced. The company estimates the cost treating the unused R/R processed water to foe
$2250 rather than $7500 to treat the wastewater through the standard treatment process.
The final cost listed on Table 8 is for the disposal of the sludge (metal precipitate).
Again this was determined by the company to be a percentage of the total costs for sludge
disposal. The fact that this is the same for the two lines without recycling options is
expected. There are two reasons why it is less when the recycling option is employed. The
company is only recycling 30% of the zinc hydroxide it recovers. The remaining 70% is
disposed with the sludges resulting from the facility treatment unit. Although 30% of the
water recovered from the R/R system is sent to the treatment unit, it is essentially clean. The
metal content of that recovered water is too low to add an appreciable quantity to the
company's waste sludge; therefore, the calculated cost for sludge disposal of the unused
precipitate from the R/R system is 70% of that for the sludge that would result from treatment
of the ANC line without the R/R option.
Table 8 shows an annual cost savings of $15,011 for switching from a CN to an ANC
process and >$70,000 when the R/R system is also added to the line; however, this is not a
totally accurate portrayal of operational costs. There are costs associated with the operation
of the R/R system. These costs are calculated to be $10,900 annually (see p. 27).
Incorporating these added costs into the overall operational costs reduces the company's
saving to $61,718 or approximately half of the normal operating expenses for the line.
Two other factors must be considered in this calculation and those are the costs
associated with the disposal of the CN bath when conversion to ANC occurs and the cost of
the design, parts, assembly, and installation of the R/R unit. These costs were provided in
30
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Table 6 (p. 25). Taking the worse case, the cost of disposal of 1,800 gallons of CN plating
bath at $20/gallon would be $36,000. This amount for disposal and the cost of the design
and installation of the R/R system are considered the capital expenses for the project
TOTAL SYSTEM COMPARISONS
The capital costs and the annual operational expenses were entered into a spreadsheet
program (General Electric 1987) that calculates a number of economic indices. The program
also uses other economic factors, such as inflation rate, in its calculations. These factors are
assumed to remain constant over the 10 year life of the project. The factors used in the
calculations for the assessment are provided in Table 9.
TABLE 9. ASSUMPTIONS FOR ECONOMIC CALCULATIONS
Item
Factor
Source
Inflation Rate
Discount Rate
Federal Tax Rate
Depreciation Schedule
Project Life
Labor Costs
Sludge Disposal Costs
Water Costs
Water Usage
Water Sewering
4%
7.72%
34%
7 years
10 years
$15/hour
$209/cubicyd
$7.56/7480 gallons
$5.59/7480 gallons
Consumer Price Index
10 year treasury bill rate +0.5%
General Electric, (1987)
General Electric, (1987)
P&H Plating Co.
P&H Plating Co.
P&H Plating Co.
Metropolitan Water
Reclamation District of Greater
Chicago ,
The assumptions from Table 9 combined with the first year's operational expenses,
including the capital costs, were used to estimate the annual expenses for the operation of the
CN line, the ANC line, and the ANC line with an active R/R system, over the course of the
project life of 10 years. The comparisons were between the existing operation (CN) and the
modification by chemical substitution (ANC), CN and ANC with recovery and recycling of
chemicals and water (R/R), and ANC and ANC with R/R.
Table 10 presents the 10 year annual breakdown for the CN line. Because these tables
were intended to show the areas of difference between the three possible plating line
configurations, costs that were essentially the same for all three systems (power and labor for
the plating operation) are not included in the calculations. Annual expenses for the ANC line
are provided in Table 11. Except for the first year of operation, when there are capital costs,
the ANC operating expenses run $15,000-$20,000 less than those for the CN line. The
31
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expenses listed in Table 12 show that the savings to the company increase by more than a
factor of 4 ($60,000-$80,000) when the R/R unit is made operational on the ANC line.
The spreadsheet used the assumptions in Table 9 and the first year's operating
expenses, including the capital costs, for each of the three plating operations to calculate the
implied rate of return, the net present value, and the payback period for the line
modifications. The results of this calculation are presented in Table 13 (Table 2 in summary).
While the replacement of CN by ANC is economically advantageous to the company,
making the change and including the recovery/recycle option results in even greater economic
benefits. Capital expenses for the system would be recovered in 18 months of operation.
The implied rate of return for the ANC + R/R option is approximately 72% with a net present
value of $281,122.
The goal of the project was to develop a closed-loop system that would achieve zero
discharge of the wastewater and total reuse of the recovered chemicals. That was not
achieved. The system that was installed, however, is simple, has substantially reduced water
usage and will have paid for itself within 1.5 years of operation. Once the initial outlay has
been recovered, operational costs can be reduced by 50% or more depending on the recycling
effort desired by the plating operation. Because verification of recovered water and
precipitate quality are necessary before recycling becomes an option, a truly closed loop
system is not possible, but a R/R unit such as the one currently in operation at P&H Plating
could be easily and inexpensively installed on ANC lines at other plating facilities with
similar or even greater economic benefit resulting from the recycling of the recovered
materials.
34
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35
-------
TABLE 13. COMPARISON OF ECONOMIC INDICES FOR THE ALKALINE NONCYANIDE PLATING
PROCESS WITH AND WITHOUT THE RECOVERY/RECYCLE SYSTEM
Index Option
ANC ANC + R/R
Capital Investment $36,000 $87,822
Payback Period 3 years 1.5 years
Net Present Value $57.500 $281,122
Implied Rate of Return 27.0% 71.9%
36
-------
REFERENCES
American Society for Testing and Materials (ASTM). Annual Book of ASTM Standards -
1990. Section 3: Metals Test Methods and Analytical Procedures. Volume 3.02.
Philadelphia, Pennsylvania, 1990. pp. 357-361.
Anderson, J. R93-2 In the Matter of: Pretreatment Update, USEPA Regulation (July 1, 1992
through December 31, 1992). Illinois Pollution Control Board, September 9, 1993.
California Department of Health Services (CDHS). Alternative Technologies for the
Minimization of Hazardous Waste. 1990. 23 pp.
Cambria, P. Rectifiers from Electroplating Engineering Handbook, 4th Edition. Lawrence J.
Durney, ed. Van Nostrand Reinhold. New York, New York, 1984. pp. 669-684.
Clesceri, L.S., A.E. Greenberg, and R.R. Trussell, eds. Standard Methods for the
Examination of Water and Wastewater. Seventeenth Edition. American Public Health
Association, American Water Works Association, and Water Pollution Control
Federation, Washington, DC, 1989.
Comfort, E.H., P. Crampton, G.H. Cushnie, D.S. Harrison, J. Kresky, C.G. Roberts, and R.D.
Smith. Centralized Treatment of Metal Finishing Wastes at a Cleveland Resource
Recovery Park. PB85-217651, U.S. Environmental Protection Agency, Cincinnati^
Ohio, 1985. 280 pp.
Cushnie, G,C, Jr. Electroplating Wastewater Pollution Control Technology. Pollution
Technology Review No. 115. Noyes Publications, Park Ridge, New Jersey. 1985.
EMPE, Inc., Consulting Engineers. Tennessee Hazardous Waste Management Study! -
Electroplaters. Tennessee Department of Economic and Community Development,
Nashville, Tennessee, 1986.
Finishers' Management (FM). Jensen Team Structures Cyanide-to-Alkaline Conversion.
37(2):14-16, 1992.
Foecke, T. Report Identifying Improved Waste Management and Waste Reduction
Opportunities. 1986.
General Electric. Financial Analysis for Waste Management Alternatives. Fairfield,
Connecticut, 1987.
37
-------
The Hazardous Waste Consultant (HWC). Waste Minimization Case Studies - Economic
Analysis of Waste Minimization Alternatives for the Metal Finishing Industry. 8(6): 1-
21 - 1-24, 1990.
Harris Publishing Company (Harris). 1992 Harris Illinois Industrial Directory. Twinsburg,
Ohio, 1992.
Kansupada, V.K. Zinc Plating Technology - Which Option is Best for You? Finishers'
Management, 1985.
Kirsch, F.W. and G.P. Looby. Case Study: Pollution Prevention in Practice: Applications for
Electroplating Technology. Pollution Prevention Review, 2(l):63-72, 1991.
Kohl, J., J. Pearson, and B. Triplett. Reducing Hazardous Waste Generation with Examples
from the Electroplating Industry. North Carolina State University, Raleigh, North
Carolina, 1985. 28 pp.
Krukowski, J. No More Wrist Slaps. Pollution Engineering, 24(20):26-33, 1992.
Lindsey, T.C. and J.M. Peden. Recycling Nickel Electroplating Rinse Waters by Low
Temperature Evaporation and Reverse Osmosis. Hazardous Waste Research and
Information Center, Champaign, Illinois, 1994. 60 pp.
Martin, T.H. Chasing those Elusive Cyanide Ions. Plating and Surface Finishing, 79(11):23-
26, 1992.
„* '
The Metropolitan Water Reclamation District of Greater Chicago (MWRDGC). Sewage and
Waste Control Ordinance as Amended September 5, 1991. Chicago, Illinois, 1991.
25 pp.
North Carolina Department of Natural Resources and Community Development (NCDNRCD).
Water Conservation for Electroplaters: Rinse Water Refuse. 1985. 5 pp.
Spearot, R.M. Review of Waste Reduction Technologies for the Metal Finishing Industry.
Finishers' Management, 38(6):34-38, 1993.
United Nations Environment Programme/Industry and Environment Office (UNEP/IEO).
Environmental Aspects of the Metal Finishing Industry: A Technical Guide. Paris,
France, 1989. 91 pp.
U.S. Bureau of the Census (Bureau). Country Business Patterns. 1989 and 1990.
Washington, D.C., 1993.
38
-------
U.S.EPA. Case Study - Moving Towards Zero. Pollution Prevention News, pp. 11. EPA
742-N-93-001, Office of Pollution Prevention and Toxics, Washington, DC, 1993.
U.S.EPA. Guides to Pollution Prevention: The Fabricated Metal Products Industry.
EPA/625/7-90/006, Center for Environmental Research Information, Cincinnati, Ohio,
1990. 76pp.
U.S.EPA. Meeting Hazardous Waste Requirements for Metal Finishers. EPA/625/4-87/018,
Center for Environmental Research Information, Cincinnati, Ohio, 1987. 52 pp.
U.S.EPA. SW - 846: Methods for Evaluating Solid Waste - Physical/Chemical Methods.
Third Edition. Office of Solid Waste and Emergency Response, Washington, DC,
1986.
U.S.EPA. Environmental Pollution Control Alternatives - Reducing Water Pollution Control
Costs in the Electroplating Industry. EPA/625/5-85/016, Industrial Technology
Division and Center for Environmental Research Information, Washington, DC and
Cincinnati, Ohio, 1985a. 62 pp.
U.S.EPA. Environmental Regulations and Technology - The Electroplating Industry.
EPA/625/10-85/001, Industrial Technology Division and Center for Environmental
Research Information, Washington, DC and Cincinnati, Ohio, 1985b. 44 pp.
U.SJBPA. Control and Treatment Technology for the Metal Finishing Industry - In-Plant
Changes. EPA/625/8-82-008, Industrial Environmental Research Laboratory,
Cincinnati, Ohio, 1982. 30 pp.
Walton, C.W. and K.J. Loos. Options for Minimizing Metal Finishing Waste. Plating and
Surface Finishing, 79(11):8-14, 1992.
Winter, B.E., and A.O. Facciolo, Jr. Industrial Hygiene and Safety from Electroplating
Engineering Handbook, 4th Edition. L.J. Durney, ed. Van Nostrand Reinhold. New
York, New York, 1984. pp. 341-351,
39
-------
APPENDIX A
ANALYTICAL QUALITY ASSURANCE
At the outset of this project data quality objectives were set and procedures put into
place to ensure that they were met. A project quality assurance plan describing the analytical
protocols was prepared and accepted. In general, these objectives were met, although
problems were encountered due to the complex nature of the samples being analyzed.
Analysis for water content and corrosion were performed by P&H's contract laboratory.
These data were never intended for use in the calculations of recovery, so quality assurance
information was not obtained.
For the analyses performed at HWRIC's laboratory the protocols established in the
quality assurance plan were used. Analytical procedures are described in detail in SW-846
(USEPA 1986). Only brief summaries are included in this report. Calibration curves were
determined each day that samples were analyzed using 5 standards (a single standard was
used for TOC determinations). Since daily sample runs generally did not exceed 20 samples,
a blank and complete calibration curve began and ended each sampling run. Duplicate
analyses and spikes were performed every 6 samples. Data from these samples were used to
assess precision and accuracy. Two check standards of known concentration were prepared
and analyzed every 6 samples to further assess accuracy and as immediate checks on the
standard curve. The analyte concentrations of these check samples were chosen to check the
accuracy of the data at both the high and low ends of the standard curve.
METAL ANALYSIS
Samples were analyzed by atomic absorption to determine metal content. Data from
these analyses are included in Appendix B. (Tables B-2, B-4, B-5, B-7, and B-8). Sludge
samples were prepared following method 3050. This method calls for digestion of the sample
in nitric acid and hydrogen peroxide. The digestate is reflexed with hydrochloric acid prior to
analysis by flame A A according to methods 7950 for zinc analyses, 7380 for iron, 7140 for
calcium and 7770 for sodium. Aqueous samples were prepared following 3010. This
procedure calls for the digestion of the sample with nitric acid prior to analysis.
These methods suggest the use of a 5-point calibration curve. This recommendation
was followed and standards were selected to fit the anticipated concentration ranges of the
samples. Because the metal concentrations of the samples go from very high (% quantities)
40
-------
in the sludge to very low (ug/L) quantities in the treated wastewaters, some samples were
diluted, prior to analysis.
In general, manufacturer's operating procedures were followed during the analyses.
Software packages which were included with the instruments were used to generate the
standard curve that was then used to calculate the concentrations of the metals in the samples.
Check samples were selected to check the upper and lower portions of the calibration curve.
Samples were analyzed in groups of 6 or less. Check samples, a reagent blank, at least one
duplicate, and one spike were analyzed with each set of 6 samples. Raw data tables are
provided in Appendix B. These data are presented as run logs, i.e. the samples (both the
unknown and the quality control) are listed as analyzed.
TOTAL ORGANIC CARBON (TOC)
Analysis for TOC was not routinely performed during the project. These analyses
were used to simply check for the presence of organic carbon that would result if brightening
agents were carried over in the recycling operations. One standard was used to calibrate the
instrument, following the manufacturer's directions. Samples were selected at random.
Because these analyses were not integral to the determination of the quality of the
recovered/recycled materials nor the quality of the plate, quality control procedures were
greatly reduced. TOC analysis was included in the original list of analyses that would be
performed'for there was a possibility organic carbon concentrations could become elevated
through the recycling efforts. The analysis of these randomly selected samples showed this
was not the case so there was no need to continue to analyze for this parameter.
The TOC determinations followed method 9060. Two different instruments Were
used, one for solids and the second for aqueous samples. Solid samples were analyzed by
combustion. A single known sample was used to check instrument performance. Instrument
software calculated TOC concentrations. Liquid samples were analyzed by wet chemical
oxidation. Again, a single standard was used to check instrument performance and calculate
the TOC content in the test samples.
ACCURACY, PRECISION, AND COMPLETENESS
Accuracy, precision, and completeness were determined for the three sets of data
reported by HWRIC's laboratory. The data sets included the analysis of zinc hydroxide
precipitate from the R/R system, the input and output samples from the initial testing of the
R/R system, and the input and output samples from the final testing of the R/R system.
41
-------
Accuracy is the agreement of a measurement or average of measurements with an
accepted reference or known material. Orie measure of the accuracy of each data set is
presented as the percent recovery of the quality control standards. This is a measure of the
agreement between the known or calculated value of the standard and the measured value.
The percent recovery is calculated as follows:
%Recovery = (Experimental Value) * (Known Value) x 100%.
The second evaluation of accuracy uses the percent recovery of spiked samples to assess the
effect of the matrix on the samples analyses. It is calculated using this formula:
%Recovery = [(Spiked Sample) - (Unspiked Sample)} * (Amount Spiked) x 100%.
Precision measures the agreement among individuals measurements of the same sample.
Precision is determined in two ways for these data sets. The precision among three or more
replicates, in this case the analyses of the quality control standards and/or triplicate sample
analyses, is calculated as percent relative standard deviation (%RSD), which is calculated as:
%RSD = $ * x x 100%, -where
x = Exj * n = t he arithmetic mean of a set of results, and
s = y^ C*i-*)2 * (»-l) = the standard deviation among replicates.
When only two values are determined, as in the case of duplicates, precision is defined as the
relative percent difference (RPD) and calculated:
KPD = (P-D * KPDJ *2]x I00%,where
RPD = Relative Percent Difference
Dj = the larger of the two observed values, and
D2 = the smaller of the two observed values.
The completeness criterion compares the number of measurements taken to the number
considered valid. A percent completeness for each of the three data sets is provided with
Tables A-l through A-3. The overall percent completeness for all of the samples analyzed
for the project is 94%, which is slightly less than desired, but acceptable for the evaluation of
the R/R system.
42
-------
TABLE A-1. QUALITY ASSURANCE (QA) DATA FOR THE ANALYSIS OF RECOVERED
PRECIPITATE OBTAINED DURING THE INITIAL EVALUATION OF THE CNT SYSTEM
Sample
Type
Check Samples
% Recovery
% RSD
Spikes
% Recovery
Duplicates
RPD
N*
4
2
4
Zinc
99
2
121
6
Iron
115
1
91
11
Metals Analyzed
Calcium
100
10
149
9
Magnesium
99
1
110
5
Completeness for data set = (200 valid) + (204 total) x 100% = 98%
'N=Number of samples analyzed
TABLE A-2. QUALITY ASSURANCE (QA) DATA FOR THE OUTPUT WATER SAMPLES OBTAINED
DURING THE INITIAL EVALUATION OF THE CNT SYSTEM
Sample Metals Analyzed
Type N* Zinc Iron
Check Samples
% Recovery 116 100
%RSD 16 7 1
Spikes
% Recovery 6 105 112
Triplicates
%RSD 6 2
Completeness for data set - (92 valid) •*• (92 total) x 100% = 100%
*N=Number of samples analyzed
43
-------
TABLE A-3. QUALITY ASSURANCE (QA) DATA FOR THE INPUT AND OUTPUT WATER SAMPLhS
OBTAINED DURING THE FINAL EVALUATION OF THE CNT SYSTEM
Sample Metal Analyzed
Type N Zinc
Check Samples
% Recovery 107
%RSD 6 3
Spikes
% Recovery 4 118
Duplicates
RPD 4 2
Completeness for data set = (57 valid) H- (67 total) x 100% = 85%
*N=Number of samples analyzed
The data summaries presented in Tables A-l through A-3 show that except for
completeness and the percent recovery of zone for the check samples analyzed with the liquids
obtained during the initial tests of the system, all of the quality assurance objectives for the
project were met. For the precipitate (solid) samples check samples percent recovery falls
within the range 80-120%, check samples %RSD is less than 20%, spike percent recovery
falls within the range 60-140%, and duplicates RPD is less than 40%. The objectives for the
liquid samples were: percent recovery range of 90-110% for check samples, %RSD less thaua
10% for check samples, percent recovery range of 75-125% for spikes, and RPD of less than
25% for duplicates. The problem with completeness resulted from a contamination problem
in the water and reagent blanks on one of the days that analyses were being performed. Trie
measured zinc content of the blanks was greater than the lowest and second lowest standard
and larger than 2 of the 6 samples analyzed in that run. Because the data evaluation occurred
some time after the analyses were performed, the cause of the blank contamination could not
be determined, these data were not used in the calculations, and it was decided that repeating
the analyses was not necessary. The valid data provided all of the needed information. The
other problem is with the accuracy of the control samples analyzed with the first set of water
samples .from the recovery system. Again, the extent of the deviation from the theoretical
was not noticed until some time after the analyses were completed. In this case, though, the
deviation from the objective was not that great and the accuracy obtained was sufficient to
use in the system evaluation, so all of the data were used.
REFERENCE STANDARDS
The laboratory did not participate in performance evaluations (PEs) during the periods
that these analyses were performed. The lab does participate in the U.S. Geological Survey's
44
-------
(USGS) performance assessment for metals on a quarterly basis. Over the course of the
project HWRIC's performance on these USGS PE samples was rated satisfactory for zinc,
iron, calcium, and magnesium. While these samples are natural waters and soils and not truly
comparable to the wastewaters and sludges analyzed for this project, they are prepared and
analyzed following the same procedures and offer the best substitute available.
Certified standards were used to prepare the calibration and check sample standards.
These were prepared several times over the course of the study from different stock solutions
and were consistently within 10% of the theoretical concentration.
DETECTION LIMITS (DL)
Concentration of metals in the samples in most cases were far above the minimum
capabilities of the instruments. This was true for all but the blanks and treated rinsewater
samples. These samples had concentrations in the ug/L range but generally at or slightly
above the DL. For this study, it was not necessary to achieve the lower limits prescribed in
the quality assurance plan, for the cleaned water was acceptable for recycle at much higher
concentration ranges. The data were verified by duplicate analyses and spikes, in addition to
blanks and check standards. All data used in the evaluation are provided in Appendix B,
45
-------
APPENDIX B
ANALYTICAL DATA
TABLE B-1. WATER CONTENT OF ZINC HYDROXIDE FROM CNT RECOVERY/RECYCLE SYSTEM
Sample No.
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
% of Water
87.84
89.63
91.87
91.07
89.19
89.53
91 .73
89.28
89.81
88.91
89.28
87.64
91.50
89.28
87.39
91.01
Sample No.
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
% of Water
86.04
88.60
88.86
88.83
90.49
89.97
92.21
88.34
87.82
89.37
92.34
92.93
93.04
89.22
86.25
64.55
46
-------
TABLE B-2. ANALYSIS OF DRIED ZINC HYDROXIDE SLUDGE SAMPLES FROM P&H PLATING CO.
Concentration %
Sample Number
P&H399
P&H400
P&H401
P&H402
P&H402DUP
P&H403
P&H404
P&H405
P&H406
P&H407
P&H408
P&H409
P&H410
P&H411
P&H411DUP
P&H412
P&H413
P&H414
P&H415
P&H416
P&H417
P&H417SP
P&H418
P&H419
P&H419DUP
P&H420
P&H421
PSH422
P&H423
P&H423SP
P&H424
P&H425
P&H426
P&H426DUP
P&H427
P&H428
P&H429
P&H430
Zinc (Zn)
70.4
69.8
47.0
55.1
51.3
60.3
59.0
64.9
62.4
69.0
59.7
65.2
67.2
64.7
64.6
58.3
72.7
72.4
75.7
72.4
71.3
60%
70.8
77.4
65.0
71.6
63.1
70.5
72.1
220%
64.9
61.8
51.4
52.3
54.5
58.6
62.4
45.5
Iron (Fe)
0.78
0.56
0.77
1.0
1.04
1.65
1.05
0.55
1.06
0.43
0.52
0.70
0.78
1.17
1.28
0.82
0.39
0.21
0.33
0.79
0.32
65%
0.31
0.44
0.28
0.72
0.26
0.29
0.48
111%
0.62
3.32
2.80
3.79
3.05
1.59
0.91
1.10
Calcium (Ca)
5.47
2.58
8.14
8.50
5.63
5.44
2.88
5.42
0.70
4.25
4.80
3.60
3.66
3.80
3.20
0.15
0.23
0.36
2.16
0.86
258%
0.93
0.80
0.60
1.00
0.74
0.86
0.65
189%
3.97
6.36
5.89
7.12
0.79
5.46
4.46
4.83
Magnesium (Mg)
4.26
4.92
4.52
2.34
2.38
2.23
2.57
1.06
1.04
0.97
1.23
1.95
1.66
1.74
1.73
1.48
0.14
0.26
0.58
1.20
0.92
340%
1.12
0.99
0.85
0.97
0.59
0.67
0.78
101%
2.49
2.10.
0.20
1.83
0.24
2.19
2.07;
1.91
DUP=Duplicate
SP=Spike
47
-------
TABLE B-3. CARBON ANALYSIS FOR RANDOMLY SELECTED ZINC HYDROXIDE SLUDGES
Sample No. Total Carbon % Total Inorganic Total Organic
(TC) Carbon % (TIC) Carbon % (TOG)"
CaCo3 (Std.)b 11.9 12.1
399 0.4 0.4 0
406 1.6 1.6 0
413 0.1 0.1 0
420 0.4 - 0.4 0
427 2.0 2.0 0
430 2.1 0.2 1.9
a TOC=TC-TIC
b Theoretical TIC=12%
48
-------
TABLE B-4. RUN LOG FOR ANALYSIS OF RINSEWATER SAMPLES (INPUT)
TAKEN DURING INITIAL TESTING OF R/R SYSTEM
P&H Sample ID#
Reagent Blank
Check Std.
Check Std.
N080PHLD78
N080PHLD63
N080PHLD66
N080PHLD75
N080PHLD70
N080PHLD71
N080PHLD70
N080PHLD70
N080PHLD71
Reagent Blank
Check Std.
Check Std.
N080PHLD74
N080PHLD62
N080PHLD79
N080PHLD67
N070PHLD58
N070PHLD59
N080PHLD67
N080PHLD67
N070PHLD59
Reagent Blank
Check Std.
Check Std.
N070PHLD51
N070PHLD54
N070PHLD50
N070PHLD55
N070PHLD50
N070PHLD50
N070PHLD55
Reagent Blank
Check Std.
Check Std.
Sample No.
RBIk
CS-1
CS-2
1
2
3
4
5
6
5D
5T
6S
RBIk
CS-1
CS-2
7
8
9
10
11
12
10D
10T
12S
RBIk
CS-1
CS-2
13
14
15
16
15D
1ST
16S
RBIk
CS-1
CS-2
pH
12.5
12.6
12.6
12.6
12.8
12.7
12.8
12.8
12.7
12.6
12.6
12.5
12.6
12.9
12.9
12.6
12.6
12.9
12.7
12.6
12.7
12.5
12.7
12.7
12.5
Zn (mg/L)
0.07
0.25
0.82
180
120
170
160
260
210
260
260
280
0.07
0.30
0.83
140
120
170
150
310
330
160
140
380
0.08
0.25
0.82
190
170
200
160
200
190
200
0.08
0.26
0.82
Fe (mg/L) ;
0.28
0.86
7.1
0.65
0.37
0.75
0.50
0.60
0.54
0.65
0.61
0.84
0.27
0.85
7.1
0.35
0.33
0.69
0.77 ;
0.33
0.23
0.77
0.77
0.53
0.28 !
0.85
7.1
0.27
0.51
0.29
0.46
0.29
0.27
0.71
0.28
1.0
7.1
CS-1 (Theoretical) = 0.25 mg Zn/L and 0.85 mg Fe/L
CS-2 (Theoretical) = 0.80 mg Zn/L and 7.1 mg Fe/L
D s Duplicate
T = Triplicate
S = Spike
49
-------
TABLE B-5. RUN LOG FOR ANALYSIS OF TREATED WATER SAMPLES (OUTPUT)
TAKEN DURING INITIAL TESTING OF R/R SYSTEM
P&H Sample ID#
Reagent Blank
Check Std.
Check Std.
N080FTLD80
N080FTLD81
N080FTLD76
N080FTLD77
N080FTLD73
N080FTLD72
N080FTLD73
N080FTLD73
N080FTLD72
Reagent Blank
Check Std.
Check Std.
N080FTLD69
N080FTLD68
N080FTLD65
N080FTLD64
N070FTLD61
N070FTLD60
N080FTLD64
N080FTLD64
N070FTLD60
Reagent Blank
Check Std.
Check Std.
N070FTLD57
N070FTLD56
N070FTLD53
N070FTLD52
N070FTLD53
N070FTLD53
N070FTLD52
Reagent Blank
Check Std.
Check Std.
Sample No.
RBIk
CS-1
CS-2
1
2
3
4
5
6
5D
5T
6S
RBIk
CS-1
CS-2
7
8
9
10
11
12
10D
10T
12S
RBIk
CS-1
CS-2
13
14
15
16
15D
15T
16S
RBIk
CS-1
CS-2
pH
10.1
10.2
10.1
10.1
10.1
10.1
10.1
10.1
10.1
10.2
10.2
10.1
10.1
10.1
10.1
10.1
10.1
10.1
10.1
10.1
10.1
10.0
10.1
10.1
10.0
Zn (mg/L)
0.01
0.30
0.80
53
92
14
15
12
12
12
12
15
0.01
0.30
0.80
10
10
2.2
2.3
6.5
6.6
2.3
2.3
8.9
0.01
0.30
0.79
37
36
6.2
6.4
6.5
6.1
8.7
0.01
N/A
0.79
Fe (mg/L)
0.01
0.27
0.80
0.98
1.4
0.32
0.32
0.21
0.20
0.20
0.22
0.50
0.01
0.27
0.81
0,13
0.13
0.24
0.27
0.09
0.11
0.27
0.26
0.36
0.02
0.28
0.82
0.79
0.71
0.13
0.13
0.13
0.13
0.40
0.03
0.28
0.81
CS-1 (Theoretical) = 0.25 mg ZN/L and 0.25 mg FE/L
CS-2 (Theoretical) = 0.80 mg ZN/L and 0.80 mg FE/L
D = Duplicate
T = Triplicate
S = Spike
50
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TABLE B-6. CONTRACT LABORATORY TOC ANALYSIS OF RINSEWATER SAMPLES
TAKEN DURING INITIAL TESTING OF R/R SYSTEM
Sample No. TOC (mg/l)
N070PHLD54
N080PHLD67
N080PHLD62
N080PHLD78
N070PHLD50
No quality assurance data provided
51
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TABLE B-7. RUN LOG FOR ANALYSIS OF ZINC IN RjNSEWATER SAMPLES TAKEN SEPTEMBER 12, 1992 AND
SEPTEMBER 19, 1992 FOR THE FJNAL EVALUATION OF THE R/R SYSTEM
Sample
Blank
Standard 1
Standard 2
Standard 3
Standard 4
Standard 5
Reagent Blank
Low Check Std.
High Check Std.
A1 Tank 3 Inlet
B1 Tank 7 Inlet
A2 Tank 3 Inlet
B2 Tank 7 Inlet
A3 Tank 3 Inlet
B3 Tank 7 Inlet
A4 Tank 3 Inlet
B4 Tank 7 Inlet
Alkaline Plating Bath
Rectifier Coolant Wafer
Cyanide Rinse 1 1 :20
Cyanide Rinse 2:00
Cyanide Rinse 2:55
A4 Tank 3 Inlet
B1 Tank 7 Inlet
Reagent Blank
Low Check Std.
High Check Std.
A1 Tank 3 Inlet
A2 Tank 3 Inlet
A3 Tank 3 Inlet
A4 Tank 3 Inlet
81 Tank 7 Inlet
B2 Tank 7 Inlet
B3 Tank 7 Inlet
B4 Tank 7 Inlet
Cyanide Rinse AM
Cyanide Rinse PM
A3 Tank 3 Inlet
B4 Tank 7 Inlet
Reagent Blank
Low Check Std.
High Check Std.
Sample Date
Sept. 12
Sept. 12
Sept 12
Sept. 12
Sept. 12
Sept 12
Sept. 12
Sept 12
Sept. 12
Sept 12
Sept. 12
Sept. 12
Sept 12
Sept 12
Sept. 12
Sept. 19
Sept. 19
Sept 19
Sept. 19
Sept 19
Sept 19
Sept 19
Sept 19
Sept 19
Sept. 19
Sept 19
Sept. 19
Lab#
Blk
Std1
Std2
Std3
Std4
StdS
RBIank
CS-L
CS-H
91-1430
91-1431
91-1432
91-1433
91-1434
91-1435
91-1436
91-1437
91-1438
91-1439
91-1440
91-1441
91^1442
91-14436D
91-14431S
RBIank
CS-L
CS-H
91-1463
91-1464
91-1465
91-1466
91-1467
91-1468
91-1469
91-1470
91-1471
91-1472
91-1465D
91-1 470S
RBIank
CS-L
CS-H
Anal.
Date
Oct. 3
Oct. 3
Oct. 3
Oct. 3
Oct. 3
Oct3
Oct 3
Oct. 3
Oct 3
Oct. 3
Oct 3
Oct. 3
Oct 3
Oct. 3
Oct 3
Oct 3
Oct 3
Oct 3
Oct 3
Oct 3
Oct 3
Oct 3
Oct 3
Oct 3
Oct. 3
Oct 3
Oct 3
Oct 3
Oct 3
Oct. 3
Oct. 3
Oct 3
Oct 3
Oct 3
Oct 3
Oct 3
Oct. 3
Oct 3
Oct. 3
Oct3
Oct 3
Oct. 3
Cone.
ug/ml
0.0
0.1
0.3
0.5
0.7
1.0
0.00
0.26
0.79
1.2
46
4.8
9.7
150
2.0
22
10
9900
0.00
320
250
170
22
52
0.00
0.27
0.81
250
180
290
270
9.7
21
32
69
210
102
290
150
0.00
0.26
0.79
Tank 3=Untreated Sample
Tank 7=Treated Sample
CS-L (Theoretical)=0.25 mg/L
CS-H (Theoretical)=0.80 mg/L
D=Duplicate
S=Spike
52
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TABLE B-8. RUN LOG FOR ANALYSIS OF ZINC IN RINSEWATER SAMPLES TAKEN
SEPTEMBER 7, 1992 AND OCTOBER 10, 1992 FOR THE FINAL EVALUATION OF THE R/R SYSTEM
Sample
Blank
Standard 1
Standard 2
Standard 3
Standard 4
Standard 5
Reagent Blank
Low Check Std.
High Check Std.
*A1 Tank 3 Inlet
*B1 Tank 7 Inlet
*A2 Tank 3 Inlet
*B2 Tank 7 Inlet
*A3 Tank 3 Inlet
*B3 Tank 7 Inlet
*A4 Tank 3 Inlet
*B4 Tank 7 Inlet
*A4 Tank 3 Inlet
*B4 Tank 7 Inlet
Reagent Blank
Low Check Std.
High Check Std.
A1 Tank 3 Inlet
B1 Tank 7 Inlet
A2 Tank 3 Inlet
B2 Tank 7 Inlet
A3 Tank 3 Inlet
B3 Tank 7 Inlet
A4 Tank 3 Inlet
B4 Tank 7 Inlet
B4 Tank 7 Inlet
B1 Tank 7 Inlet
Reagent Blank
Low Check Std.
High Check Std.
Sample Date
Sept. 27
Sept. 27
Sept. 27
Sept. 27
Sept. 27
Sept. 27
Sept. 27
Sept. 27
Sept. 27
Sept. 27
Oct. 10
Oct. 10
Oct. 10
Oct. 10
Oct. 10
Oct. 10
Oct. 10
Oct. 10
Oct. 10
Oct. 10
Lab#
Blk
Std1
Std2
Std3
Std4
Std5
RBIank
CS-L
CS-H
91-1476
91-1477
91-1478
91-1479
91-1480
91-1481
91-1482
91-1483
91-1482D
91-1483S
RBIank
CS-L
CS-H
91-1486
91-1487
91-1488
91-1489
91-1490
91-1491
91-1492
91-1493
91-1493D
91-1487S
RBIank
CS-L
CS-H
Anal. Date
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Oct. 17
Cone.
ug/ml
0.0
0.1
0.3
0.5
0.7
1.0
0.30
0.29
0.79
30
10
20
0.00
50
39
40
7.0
40
56
0.00
0.28
0.80
25
2.9
30
2.9
37
6.8
58
3.0
3.3
71
0.10
0.28
0.81
"High blank at start of run-data not used to calculate means in Table 5
Tank 3=Untreated sample
Tank 7=Treated sample
CS-L (Theoretical)=0.25 mg/L
CS-H (Theoretical)=0.80 mg/L
D=Duplicate
S=Spike
53
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