United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
*
Research and Development
EPA-600/S2-81-153 Oct. 1981
Project Summary
Assessment of Emerging
Technologies for Metal
Finishing Pollution Control
Three Case Studies
P. Militello
The researcli program described in
this report was initiated with the
objective of bringing information
concerning performance and cost of
new wastewater treatment technol-
ogies to the ittention of the metal
finishing comr lunity.
Many novel t pproaches to treatment
of electroplatii g wastewater had been
evaluated base d on available informa-
tion under an sarlier effort. The most
promising of these were selected for
further investigation to include sam-
pling, perforrr ance verification, and
cost analysis. The report presents the
results of that investigation for the
three emerging i technologies selected.
The treatment methods studied
included a system for treatment of
electroplating wastes with ozone, a
technique for chrome recovery by ion
transfer, and a method of treating
mixed wastestreams using ion ex-
change. Performance of each of these
technologies was evaluated through
sampling and analysis of prototype
operation under normal production
conditions. Performance data and
cost projections for each system are
presented.
Each of the three systems investi-
gated was found to hold promise for
improved cost-effectiveness of waste-
water treatment for appropriate appli-
cations.
This Project Summary was developed
by EPA's Industrial Environmental
Research Laboratory, Cincinnati, OH.
to announce key findings of the re-
search project that is fully documented
in a separate report of the same title
(see Project Report ordering informa-
tion at back).
Introduction
This work under EPA Contract No. 68-
03-2907, Work Effort 09 represents a
continuation of EPA Contract 68-03-
2672, WA 52. The objective of the
earlier effort was to identify new or
novel wastewater treatment techno-
logies. The technologies reviewed were
subjected to a worth assessment which
evaluated factors such as costs, energy
consumption, effectiveness on target
pollutants, and degree of applicability
against conventional precipitation
treatment methods. The assessment
considered technologies in all stages of
development. Eventually, the first phase
of the project identified promising
projects in three categories of develop-
ment stage: already demonstrated, in a
research and development stage, and in
a pilot stage.
The objective of the second phase of
this project reported on herein is to
characterize the highest ranking tech-
nologies in the already demonstrated
category by gathering performance and
cost data under actual operating condi-
tions at production metal finishing
facilities. This report examines three
treatment systems identified as emer-
-------
ging technologies of significant promise
for the electroplater. The technologies
are presented in the form of case
histories and have been evaluated with
respect to their capability to reliably
remove pollutants, the initial costs of
installation, and the day-to-day costs of
operating the system including labor,
utilities, treatment chemicals, and
sludge disposal.
The systems under consideration
here were each sampled over 4 or 5
consecutive days of operation under
normal production conditions. Four grab
samples of influent and effluent of the
system were collected over the produc-
tion day at each plant for specific
pollutant parameters. In addition,
samples were collected when possible
prior to and following specific unit
processes to establish their performance.
The basic cost data presented were
supplied by the manufacturers.
The systems evaluated, as selected
during the earlier phase of this effort,
were:
• The Ozodyne treatment system
• The ChromeNapper™ chrome re-
covery system
• The Rinse-Loop ion exchange
system
Results
A schematic of the Ozodyne system
as installed at San Diego Plating is
shown in Figure 1. The key feature of
this treatment system is the method
whereby ozone is introduced. As shown
in Figure 1, the wastewater containing
dissolved ozone and ozone gas enters a
1136-liter ozone reactor. The waste-
water is injected tangentially into the
rim of a small spinning stainless steel
bowl. Rim speeds can be as high as
40,000 rpm. The wastewater is shat-
tered into a cloud or mist, thereby
enormously increasing the surface area
of contact between the ozone and other
molecules, including cyanide. From the
reactor, the wastewater is pumped to a
rotary vacuum precoat filter where it is
dewatered. Solids are collected for
disposal while filtered effluent issentto
the sewer.
To evaluate the performance of the
treatment system at San Diego Plating,
effluent was monitored over a 4-day
period. In addition, sampling was done
at the location of the influent to the
system and at specific locations before
and after each treatment step. A
summary of the results of the sampling
program is presented in Table 1.
The ChromeNapper™ system is a new
electrolytic method designed to reduce
the cost of chrome recovery. The system
employs what the manufacturer calls an
electrolytic ion transfer membrane. The
membranes are a proprietary substance
which requires no implanting of ion
exchange resin as in electrodialysis
membranes.
In addition, instead of using thin
membranes separating three compart-
ments as in a conventional electro-
dialysis cell, the new system uses a
single, thick (1.2 cm) ion-permeable
membrane which separates two com-
partments. Figure 2 shows a schematic
representation of a membrane module.
The membrane surrounds an inner
compartment approximately 3.4 liters in
volume. Platinum-plated titanium
anodes are inserted through the top of
the module which contains the re-
covered chromic acid/sulfuric acid
anolyte. The outside of the membrane is
wrapped in a stainless steel mesh
cathode. Rinsewater is the catholyte
solution. Ion transfer and concentration
of the chromic acid are accomplished by
applying a direct current between the
anodes and the mesh cathodes on the
outside of each cell. Chromic acid
concentrates in the anode compartment
of the cell while treated dilute rinse-
water is returned to the rinse tanks.
The ChromeNapper™ system applica-
tion in this study was markedly different
than the other two technologies investi-
gated in that the ChromeNapper was
dedicated to the chromium line in a
closed-loop mode for the purpose of
Table 1. Summary of Sampling Results San Diego Plating
Influent
Effluent
Parameter
Range
Average
Range
Average'
Average Removal
Cyanide
Total chrome
Copper
Nickel
TSS
PH
3.75
6.62
33.0
60.0
559
12.2
- 0.05
• 0.82
- 5.05
- 10.2
-35
- 3.4
1.02
1.41
9.45
20.32
135
6.4'
0.87
1.55
1.32
0.37
93
12.4
- <0.02
- 0.05
- 0.04
- <0. 10
-<1
- 5.8
0.08
0.40
0.05
0.13
11.6
8.4"
>92.5
>71.6
99.5
>99.4
>91.5
—
"Median.
Average solids content of sludge = 74 percent.
Influent and effluent values, except pH. in mg/l.
Lime
Bin
Plant
Wastes
| Holding Tank
I
Mixing Tank
Air Compressor/
Ozone Generator
Rotary
Vacuum
Filter
Filtered
Wastewater
-»• to
Sewer
Sludge
to
Disposal
Figure 1. Diagram of treatment system at San Diego Plating.
2
-------
recycle reuse as opposed to the end-of-
pipe applications of the other two
systems. In the closed-loop mode,
ChromeNapper's purpose was to main-
tain a relatively constant chrome
concentration in the final rinse, with no
discharge of rinse water to waste. Thus,
as the chrome concentration increased
from dragout, the ChromeNapper re-
moved the excess.
Sampling was conducted over a 5-day
period at U.S. Plating. A summary of the
sampling results, presented in Table 2,
shows the ranges of influent and
effluent concentrations encountered as
well as averages for the sampling
period. Influent to the recovery system
is from the final rinse tank. Effluent from
the recovery unit is returned to the final
rinse. The flow rate through the
ChromeNapper™ system is chosen to be
such a value that the chrome concentra-
tion into and out of the unit is held
nearly constant. Table 2 shows that this
is being accomplished.
The Rinse-Loop ion exchange treat-
ment system installed at Chicago
Modern Plating is markedly different
from any other ion exchange system
used for treating industrial waste-
streams in that it treats a mixed waste-
stream containing both heavy metals
and cyanide with layers of resins in a
single column. Typical ion exchange
systems completely deionize waste-
water, replacing cations with hydrogen
ions and anions with hydroxyl ions. The
system at Chicago Modern, however,
uses weak- and strong-acid cation
resins in the sodium form and strong-
base anion resins in the hydroxyl form.
The weak-acid resin is selective for
cations which include toxic metals (in
addition to calcium and magnesium)
and exchanges its sodium ions for those
in the wastewater. The anion resin
removes cyanide, chromate, and other
anionic metal complexes from the
wastewater. It is this arrangement of
resins which allows the treatment of the
combined wastestream. A schematic of
the Rinse-Loop system is shown in
Figure 3.
Table 3 is a summary of the analytical
results from sampling the ion exchange
portion of the treatment system. The ion
exchange columns performed well
except when resins were allowed to
become so saturated that breakthrough
occurred, causing high concentrations
of metals in the discharge. For instance,
Samples 1 through 5 showed con-
sistently low concentrations of pol-
lutants regardless of influent concen-
lon Transfer Membrane
Stainless Steel
Mesh Cathode
From
Rinsetank
' Titanium Anode
X
~\
\ f
r
/-Anolyte Solution /
/ /
Y /
1 y-
T
- Recycled
Rinsewater
• Treatment
Tank
Rinsetank
Figure 2. A membrane module - assembled.
Wastewater
NaOH
bHi
Collection Sump
Ion Exchange
Columns
Wastewater
/X Discharge
Regenerants , N*°"
Water
Reuse
Water Reuse
Suspended Solids
Filters
NaHSOa
I Solids ^Sludge
Separation
Batch Treatment
H202
-UV-
Waste water Discharge.
Figure 3. Rinse-loop system.
trations. However, Sample 6 (taken on
Day 2) representing an on-stream time
of 11 to 12 hours for the columns,
showed a significant increase in effluent
concentrations. After regeneration,
Sample 7 once again generally showed
low levels of metals and cyanide.
Conclusions
Specific conclusions with regard to
each of the systems evaluated follow.
The Ozodyne System at
San Diego Plating
The system exhibited reliable per-
formance when operating on mixed
wastewaters, reducing effluent concen-
trations of cyanide, metals, and total
suspended solids to very low levels,
often less than the limits of detectability.
The vacuum filter employed as part of
the system was able consistently to
dewater the resulting sludge to a very
dry 75 percent solids content.
The system should become highly
competitive on a cost basis with con-
ventional treatment as sludge disposal
costs escalate.
The ChromeNapper™ System
at U.S. Plating
The system exhibited reliable per-
formance on a continuous unattended
basis over the several days of monitor-
ing, successfully recovering and return-
ing to the plating tank all chrome other
than that plated on the workpiece.
Very small quantities of solid waste
were produced {about 1.89 liters of
sludge per week), resulting in negligible
sludge disposal cost.
Economic comparison with conven-
tional evaporative recovery shows the
-------
ChromeNapper™ system to be highly
attractive.
The Rinse-Loop System at
Chicago Modern Plating
Although the system was plagued
with operational difficulties from ancil-
lary equipment, the basic ion exchange
technology operated satisfactorily on
the mixed wastewaters during those
limited periods when it was possible to
pay sufficient attention to maintenance.
Considerable operator attention was
required. The system as installed at
Chicago Modern Plating was operating
in a shake-down mode. The system in its
observed embodiment was not func-
tioning in such a manner that its
transfer to other environments can be
recommended at this time.
The cost comparison with conven-
tional technology shows no advantage
for the Rinse-Loop system. However,
the ability to achieve consistent opera-
tion with less operator attention would
change that conclusion.
Table 2. Summary of Sampling Results at U.S. Plating
Influent to
ChromeNapper™
Effluent from
ChromeNapper™
Parameter
Range
Average
Range
Average
Total chrome
Hexavalent
chrome
Nickel
pH
17.5 -5.0
9.5 - 1.8
4.35 - 1.68
8.6 - 7.2
11.5
6.2
3.1
7.8'
16.0 -3.5
11.1 - 1.60
4.22 - 1.78
8.6 - 7.6
9.9
5.4
2.9
8.0"
'Median.
All values, except pH, in mg/l.
Table 3. Summary of Sampling Results of Ion Exchange Unit at Chicago
Modern Plating
Influent
Parameter
Cyanide
Total chromium
Copper
Nickel
Zinc
TSS
pH
Range
25.5 -
32.2 -
2.50-
13.2 -
46.0 -
360 -
8.6 -
4.4
2.04
0.50
1.60
13.2
7.0
3.0
Average
13.63
11.03
1.29
5.45
25.23
91.0
6.7'
Effluent
Range
10.0
24.0
11.0
6.7
56M
456
11.8
- 1.0
- 1.30
-0.23
10
38
-;.o
-6.3
i
Average
3.48
6.40
1.16
1.4
9.43
46.8
8.2'
Average %
Removal
74.5
42
10.1
74.2
62.6
48.6
—
'Median.
Influent and effluent values, except pH, in mg/l.
P. Militello is with CENTEC Corporation, Reston, VA 22090.
Roger Wilmoth is the EPA Project Officer (see below).
The complete report, entitled "Assessment of Emerging Technologies for Metal
Finishing Pollution Control: Three Case Studies," (Order No. PB 81-244 485;
Cost: $8.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
it US GOVERNMENT PRINTING OFFICE, 1981 — 559-017/7369
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