United States
Environmental Protection
Agency
 Industrial Environmental Research
 Laboratory
 Cincinnati OH 45268
Research and Development
 EPA-600/S2-83-122  Jan. 1984
Project  Summary
Electroplating  Plant  Operating
Conditions  Related  to
Wastewater Sludge Leachability
A. Procko, E. Handel, and M. Moskowitz
  The objective of this project was to
characterize the operating variables and
wastewater sludges  from  six
electroplating plants conducting a wide
variety of plating operations so that the
information  developed  would  be
applicable on an industry-wide basis.
The  results of the study in  which
untreated wastewaters were collected
from each of six AES member plants,
chemically treated to  provide solid
waste sludges are presented. The solids
were  separated,  and the effluents
analyzed for hazardous metals. All of
the sludges  were  subjected to the
ASTM  "Method  A"  extraction
procedure and hazardous  metals
analyses  were  conducted  on  the
leachate. During the study, the EPA
Extraction  Procedure  (EPA-EP) was
distributed nationally. As the EPA-EP
was   one  test  of  the   hazardous
properties  of  electroplating sludges
under the Resource Conservation and
Recovery Act  (RCRA),  the   EPA-
EP tests, rather than the ASTM Method
A extraction procedure, were replicated
for the six plants. All tests, chemical
treatment,  pH,  separation, sludges
generation, and extraction procedures
were replicated. An in-depth statistical
study was also performed of the analyt-
ical  data for  which  sufficient
information was available.
  This Project Summary was developed
by  EPA's  Industrial  Environmental
Research Laboratory. Cincinnati, OH.
to announce  key findings of the
research  project  that is  fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
 Background
   An earlier  study,* from which the
 current study developed, thoroughly
 investigated  the wastewaters  and
 attendant sludges from 12 electroplating
 shops. To utilize the data generated from
 the earlier study, six of the participating
 plating  shops were  selected for this
 current project. Selection was based on
 the  variety of   metals  utilized, the
 wastewater treatment system, and the
 leaching characteristics  of the plants'
 sludge. The presence of cadmium  in the
 plants' wastewater was highly desirable
 as cadmium appears to be a problem with
 regard to its leaching characteristics. The
 facilities selected  for this study showed
 significant quantities  of cadmium,
 chromium,  nickel, zinc,  copper,  and
 aluminum present in their wastewater
 and  sludge. Two additional  selection
 factors  included:  1)  good  cooperation
 from  plant management, and 2) the
 plants' sludge had U.S.  Environmental
 Protection Agency - Extraction Procedures
 (EPA-EP) extract levels above the haz-
 ardous limits. This last factor was con-
 sidered to demonstrate the benefits of the
 current project, if indeed, the sludges
 could be rendered nonhazardous by EPA's
 definition.

 Approach
   The purpose of the overall test program
 was  to determine  the effect  of
 wastewater treatment chemicals and the
 pH on the  leaching  characteristics of
"Meredith, J. W., J. A. McCarthy, and A. Procko.
 Electroplating Wastewater Sludge Characterization.
 EPA-600/2-81-064, U.S. Environmental Protection
 Agency, Cincinnati, Ohio, May 1981.

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sludges generated. The  effect of the
treatment chemicals on the dewaterabil-
ity  of the  sludges  by  filtering  and
centrifuging was also to be determined.
As a means to accomplish these goals, a
detailed test plan was prepared  that
covered: (1) wastewater preparation; (2)
simulation  of the plant treatment; (3)
screening tests; (4) dewatering tests; and
(5) analysis. Screening tests were to be
performed to determine the combination
of precipitation  chemical and pH which
would produce  a sludge with  the  best
leaching  characteristics  without
reducing effluent quality. Dewatering of
the sludge produced by each treatment
chemical followed, utilizing the  pH value
at which each chemical performed  best
during the screening tests.

  Screening tests were conducted to
determine  the  relationship   between
treatment chemical and pH on the treat-
ment system effluent and on the extract
from the sludges produced. The method
utilized to achieve these goals was to take
actual untreated  electroplating waste-
waters  and  treat  them  with  three
common neutralization chemicals: sodi-
um hydroxide (NaOH), soda ash (Na2CO3)
and  lime (CaO). Tests  were  conducted
with  each  of these chemicals on the
untreated  plant wastewater  with pH's
adjusted to 8.5 and 10 (7, 8.5, and 10 for
Plant 7). The wastewater was treated in
a manner similar to the plants' treatment
system  (except  for  the  change  in
chemicals and  pH) so that the  plants
could easily implement any recommend-
ed changes.  Individual waste  streams
were m ixed i n the proper proportions, and
kept  agitated while pH was  adjusted.
Appropriate retention times were used,
and  after flocculation  the mixture was
allowed  to  settle. The water  layer
(overflow) was decanted and analyzed for
its metal content and  the  sludge layer
(underflow)  was  vacuum  filtered. An
analysis of the filtrate for metals was
performed for comparison to the plant
effluent. The sludge cake was then sub-
jected to the American Society for Testing
and  Materials Method "A",  extraction
procedures (ASTM-A)  and  EPA-EP, the
extract of which was also analyzed for
metals (Figure 1).
  To study the leaching characteristics of
the screening test sludges, a portion of
each sludge after filtering was washed in
a filter funnel with 200 ml of deionized
water and again vacuum filtered and the
sludge subjected to the ASTM-A  and
EPA-EP.  The washing  water was  also
analyzed for metals.
                                Combined
                                Untreated
                                Wastewater
          CaO. NaOH.
          or Na2CO3
pH Adjustment
  Flocculant
   Addition
   Settling
Vacuum
Filter


Interstitial
Water
                                                 J_L
Filtrate


Wash
 Figure 1,    Test program and analytical plan.
Results
  For Plant 2, at pH 10.0 more than 98
percent of  the  cadmium  had been
removed  by treatment. Chromium  and
zinc were removed from the effluent with
a 99+ percent efficiency. At this pH, CaO
showed the lowest  metal  levels in the
effluent,  although  the  difference is
slight and although the metals did not
resolubilize and leach out during  the
ASTM-A procedure, the lower pH of the
EPA-EP caused Plant 2 to fail the EPA-EP
based on cadmium levels. Results of the
EPA-EP at  pH 8.5 showed lower metal
levels, but failed to pass the EPA-EP test.
The chromium extract also failed the first
time,  but passed  during the replication
phase. Chromium levels in the effluent
and  EPA-EP extract were not affected
very  much  by  pH or  chemical, except
when Na2C03 was used. With Na2C03,
chromium was  an order of  magnitude
higher in the EPA-EP extract.
           A similar analysis for Plant 3 shows
         cadmium  and  chromium  removal
         efficiencies of 91 and 68 percent, respec-
         tively, at pH 8.5. At pH 10, cadmium and
         chromium removal efficiencies were 93
         percent and 56 percent. At either pH, the
         plant's sludge failed the EPA-EP based on
         cadmium. However, cadmium performed
         very well during the ASTM-A procedure
         by not resolubilizing and leaching out, as
         chromium did. Chromium levels in the
         plant effluent were more affected by pH
         than by chemical,  while cadmium was
         affected by both. Results of the EPA-EP
         testing showed 1000 times higher levels
         of cadmium to be present than did results
         of the ASTM-A. Chromium levels did not
         vary with the two tests a nd appeared to be
         independent  of  chemical,  and  only
         slightly dependent on pH.
           For Plant 4, at pH  10 chromium was
         removed from the  effluent with an 81-
         percent efficiency,  copper was removed

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with 84-percent efficiency, and  nickel
was reduced by 85 percent.  Although
CaO did not show a clear superiority with
the effluent samples, it was most clearly
the best overall performer for the EPA-EP
and ASTM-A testing. Plant 4 was one of
two plants that would have passed the
EPA-EP based on these screening tests
At a treatment pH of 10, metal levels in
the plant  effluent and EPA-EP extracts
were  always lower when  using CaO.
Although the metals did not resolubilize
and leach  out during the ASTM-A proce-
dure, the lower pH of the EPA-EP caused
considerably higher metals levels in the
extract. Metal levels were higher by two
orders of magnitude in some cases.
  For Plant 6, at pH 8.5 chromium was
reduced by 99 percent and nickel by 97
percent in the plant effluent. Chrome in
the untreated wastewater was 21/2 times
higher than  nickel,  although  this
difference was not evident in  the plant
effluent. Results of the ASTM-A on the
plant   sludges  showed  no significant
leaching for either chromium  or nickel.
During the EPA-EP greater quantities of
metals were seen to leach in some cases
by  as  much as 100-fold. The plant's
sludge did not consistently pass the EPA-
EP. During the first series of tests,  all
sludge samples passed. However, at pH
8.5 two samples failed during  the repli-
cation, based on chromium. Best results
for the EPA-EP were obtained with treat-
ment at pH 10.
  For Plant  7, at pH 8.5  more than 97
percent of  the  cadmium had  been
removed by  treatment. It is also evident
that the cadmium had not resolubilized
and leached out of the sludge during the
ASTM-A procedure. Copper was removed
from the effluent at approximately a 95-
percent efficiency. With the exception of
the lime test at pH 10, the copper found in
the ASTM-A extract did not resolubilize to
a  large  extent. The  exception  noted
leached at a concentration three to four
times  higher  than   the   copper
concentration  in  the  untreated water.
Chromium, nickel, and zinc were present
in much higher quantities in the untreat-
ed wastewater than were cadmium and
copper. Chromium was removed from the
water  at  approximately  a 98-percent
efficiency  regardless of chemical or pH.
The quantity leached, as measured by the
ASTM-A extraction procedure,  tended to
decrease  as the  pH of the treatment
increased. The removal of nickel from the
wastewater  is very obviously dependent
on  pH and  only slightly  dependent  on
treatment, chemical   with  NaOH
performing somewhat more effectively
than CaO or Na2C03 as pH increased.
Removal  rates were approximately  90
percent at pH 8.5. Nickel levels  in the
sludge leachate were affected by both pH
and treatment chemical. At  a treatment
pH  of 10  both the  CaO  and  NaOH
generated sludges  leached very high
levels of nickel while the Na2CO3 sludge
leached less by a  factor  of 10. Zinc
removal   from  the  wastewate.r
approached   98  percent   with  little
difference between chemicals and with
minimal pH effects. Sludge leaching test
results varied with respect to treatment
chemicals.
  During the screening tests for Plant 7,
the EPA-EP was not performed. Instead, a
series of leaching tests were performed
on larger batch samples prepared at the
pH value which gave  best  results with
each  treatment chemical  during  the
screening tests. In the leaching tests, as
with the screening tests for this plant,
none of the metals seemed to resolubilize
and leach out of the sludge during the
ASTM-A  procedure. Metal levels in the
EPA-EP were generally higher than the
ASTM results.
  In  order to derive a measure  of the
statistical significance of these Plant 7
large   batch  test  results,  the  ASTM
procedure was applied to washed sludge
precipitated   by each  of  the  three
chemicals a  total of three  times. This
replication  provided   the   ability  to
calculate the experimental variation due
to chance alone. The test for statistical
significance  is based on the ratio of the
variation  in  leachate concentration (for
each metal) from one treatment chemical
to another to the variation due to chance
(the   F-statistic).   Any  observed
dependence  on  treatment  chemical is
significant if this ratio is large enough.
  A one-way analysis of variance was
performed based on the results. There
were significant results at the 99-percent
level.  The dependence of nickel concen-
tration in the leachate on the treatment
chemical was signf icant at the 95-percent
level.
  Results for Plant 8 at pH  8.5 indicate
that  chromium  was  removed  by  96
percent, copper by 97 percent, and nickel
by  96 percent from  the  untreated
wastewater. The plant effluent results
were  best when using  CaO. The  use of
NazCOs always gave higher metal con-
centrations  in the effluent  by at least
tenfold over the CaO results. The ASTM-
A procedure did not cause the metals to
resolubilize and leach out as  did the EPA-
EP. The sludge from this plant failed the
EPA-EP on   the  basis of  chromium.
Although  the  sludge  would  still have
failed the EPA-EP, less chromium leach-
ing occurred when treatment was with
Na2C03. If nickel were to be considered a
hazardous material under RCRA, the use
of Na2CO3 for treatment would need to be
more thoroughly investigated as it works
better for some metals than for others.
   It should be remembered that direct
comparisons between the EPA  and the
ASTM-A extraction procedures are  not
possible due to the differences in the
amount of dilution water  used in the
respective tests. In the tests done during
this part of the study, the EPA-EP extracts
had a much higher water-to-solids ratio
than the ASTM-A tests.
  The analytical results of plant effluent
and sludge filtrate show that the sludge's
interstitial  water   (filtrate) had metal
levels  lower  than  the  effluent. The
kinetics of the  precipitation reaction, are
initially  rapid,  but very  slow to reach
equilibrium  - the point  at  which
precipitation   essentially  stops. The
interstitial waters are in  direct contact
with the sludge particles for a longertime
than the effluent  waters  and therefore
have  more  opportunities    to take
advantage  of nucleation sites  for
precipitation. The  net result is a lower
level of metals in the interstitial water.
This theory is reinforced by the observa-
tion that the filtrate from the washed
sludges had metal levels lower than the
filtrate  from  unwashed  sludge. It  is
assumed that  equilibrium had  not yet
been reached.
  An  unexpected  observation was that
for most cases cadmium and zinc levels in
the EPA-EP extract were higher with the
washed sludges than with the unwashed
sludges.  Chromium  and  nickel levels
were  generally lower  in  the  EPA-EP
extract of the washed sludge than in the
unwashed sludges. It has been assumed
that washing with deionized water would
flush  out the high metal levels expected
to be found  in the interstitial  water.
Similar mixed  results were obtained for
washed and unwashed sludges during
the ASTM-A extraction where pH was not
maintained. This seemed to indicate that
this phenomenon  was not pH related. It
was apparent that washing sludges had
no benefit from a teachability standpoint,
and  may actually  have  caused  higher
leaching  if   the   sludge  contained
cadmium.
  Certain observations appeared for one
plant  but could not be broadly applied to
others in this study. An example of this
comes from Plant 7. In every case except
the unwashed cadmium  sample,  the

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sludges generated by Na2C03 had higher
metal levels in the EPA-EP extract than
did those produced by CaO or NaOH. This
effect was especially notable for chrom-
ium and zinc. These and other observa-
tions, as mentioned above, could not be
applied to other plants in the study.
  The effect of treatment chemical on the
solids content of the sludges showed that
calcium oxide,  in  general, resulted  in
treated wastewater streams with a higher
total  solids (TS)  content  while  NaOH
resulted in the  lowest TS.  For CaO and
Na2C03, the TS also tended to increase
directly with pH, while TS was basically
unaffected  by  pH  for  NaOH.  Three
treatment pH's were studied for Plant 7.
With  CaO  and  NaOH the  suspended
solids (SS) reached a maximum at pH 8.5
and then dropped off as  the pH was
increased to 10. SS increased with pH for
Na2C03.
Conclusions
  The conclusions drawn as a result of
tests conducted and observations made
are valid only to the  plants that  were
sampled; however, it  is likely that the
results will be generically useful to many
electroplating shops with similar waste-
water characteristics.
  Considerable lack of agreement was
found between the analytical results for
replicate samples prepared by the same
technique.  This scattering  effect gives a
surprisingly high background or random
variation.   This  is  especially true in
samples  containing  chromium  (+6).
Against such a background, only rather
large changes in sludge teachability could
be said to  correlate to given  treatment
parameters with statistical significance.
In spite of this masking  effect, some
correlations appeared to be significant,
and the following conclusions can be
drawn from the results:
  • In the  screening tests, the ability of
    wastewater treatment variables to
    influence extract quality by variation
    of  treatment  parameters   was
    apparently plant specific. The ability
    to influence extract quality appears
    to  vary  among  metals  under
    consideration.

  • Optimum  flocculant and  flocculant
    concentration were determined for
    each plant's wastewater.  A simple
    jar test was  developed  to enable
    plant  operators  to do  their  own
    evaluations.
  • The  treatment  chemical  and  pH
    affected the solids content of the
    wastewater  sludges.  The  higher
    solids sludge was produced by CaO
    at pH 10. Less solids were produced
    by NaOH and Na2C03 and were the
    same at pH 8.5 and 10.

  • The teachability of metals was lower
    when performed  by the ASTM-A
    extraction procedure than  by the
    EPA-EP. The pH  that produced the
    least leaching was different for each
    plant. The parameters (pH, treatment
    chemical, or interaction)that showed
    a statistical significance for a  plant
    can only be said to be significant for
    that particular plant. No generalities
    could  be found to apply to sludge
    teachability.

  • The  interstitial  of  free water
    associated  with  the  sludges  had
    lower metal levels than the effluent
    waters.

  • The precipitation chemical had little
    effect on sludge dewatering by centri-
    fuge and vacuum filtration. The fresh
    sludges that dewatered fastest dur-
    ing vacuum filtration all were at pH
    8.5.  In  most cases, fresh sludge
    dewatered faster than aged sludge
    though not exclusively. Each plant's
    sludge behaved differently.

  • No quick acceptance test related to
    the EPA-EP was found that could be
    broadly  applied  to all plants.  Each
    individual plant   may  be  able to
    develop  a quick acceptance test that
    applies to its own sjudge. However,
    potential for development of a quick-
    acceptance  test   for  segregated
    landfills (ASTM-A) was discovered.

  During the  sampling  portion of the
study, it was observed that many waste
treatment areas within the electroplating
shops were not being operated as well as
the  equipment  would  allow.  Control
instrumentation in some shops was  not
being properly maintained and therefore
could not treat the wastewater properly.
In other shops, important indicators were
missing  so  that the effectiveness of
treatment was never known.
Recommendations
  The  following recommendations are
based on observations made during the
testing and engineering evaluations  of
the data.
• Additional data should be obtained
  and necessary analysis performed in
  order to derive a  quick acceptance m
  test  for  operators  of segregated "
  nonhazardous waste landfills, based
  on  the  significant  correlations
  between filtrate and ASTM-A extract
  results found in the present study.

• The testing  procedures  and  their
  evaluations should be incorporated
  into  a  "Standard   Electroplaters
  Wastewater Evaluation Procedures,"
  which can be of general interest and
  value  to  individual plant operators
  who wish to make their own in-plant
  studies.

• To  determine the   validity  and
  magnitude  of some  of  the  more
  positive conclusions, such as the use
  of CaO or NaOH, selection of pH, the
  use of selected flocculants, etc., it is
  recommended that these variables
  be  studied  at one  electroplating
  plant.  The  study  would  involve
  operating the plant under  existing
  conditions, and then operating for a
  week  at  steady state with one  or
  more selected changes. The testing
  of plant  effluents and wastwater
  sludges would be analyzed and the
  data evaluated in the same manner
  as described in this report.

• The data for each plant participating
  in the study  was  given to  plant
  management  with  a  request  for
  comments,  suggestions   and
  criticism. No replies were received.
  Perhaps the American Electroplaters'
  Society might  be of  assistance  in
  obtaining feedback,  even if it is of
  general nature.

• A study to determine the "in-practice"
  variability of the EPA-EP  and the
  ASTM-A should be undertaken. This
  request has  come from many others
  using the two  procedures, and the
  data from this report also indicates
  the need for such a study.
                                                                                                                      0

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    A. Procko. E. Handel, and M. Moskowitz are with CENTEC Corporation, Reston,
       WV22090.
     Thomas J. Powers is the EPA Project Officer (see below).
     The complete report, entitled "Electroplating Plant Operating Conditions Related
       to Waste water Sludge teachability," (Order No. PB 84-120 781; Cost: $19.00,
       subject to change) will be available only from:
            National Technical Information Service
            5285 Port Royal Road
            Springfield, V'A 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
                                                                            Illi  A

United States
Environmental Protection
Agency
                  Center for Environmental Research
                  Information
                  Cincinnati OH 45268

Official Business
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                             it  60604
                                                                                   U.S. GOVERNMENT PRINTING OFFICE: 1984-759-102/843

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