United States
                   Environmental Protection
                   Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
                   Research and Development
EPA/600/SR-95/087    August 1995
vvEPA         Project Summary
                    Chromate  Recovery  from
                    Chromating  Rinsewater in  the
                    Metal-Finishing  Industry
                   Arun R. Gavaskar, Robert F. Olfenbuttel, and Eric H. Drescher
                     The recovery system evaluated in this
                   study combines various  aspects of
                   vacuum evaporation and flash distilla-
                   tion. It provides a continuous supply of
                   good  quality rinsewater  to  the
                   chromating line at the  Quality Rolling
                   and Dehurring Co. (QRD). Recircula-
                   tion prevents nearly 450,000 gal of wa-
                   ter  from going to waste  every year.
                   Contaminants removed from the circu-
                   lating  water  include chromium, zinc,
                   and other dissolved solids. Contami-
                   nants are concentrated in a tiny waste
                   stream (one 55-gal drum) and disposed
                   of. Because QRD uses three different
                   chromate formulations on a single
                   chromating line, this concentrate could
                   not be reused. At  plants  that use a
                   single formulation,  reuse should  be
                   possible. Because wastewater (requir-
                   ing treatment) is not generated, the re-
                   covery system reduces operating costs.
                   At QRD, the return on investment was
                   sufficient for the initial capital outlay to
                   be recovered in approximately  4 yr.
                     This Project Summary was developed
                   by EPA's National Risk Management
                   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
                     The goal of the U.S. Environmental Pro-
                   tection Agency's (EPA) 33/50 Program is
                   to promote voluntary reductions in the re-
                   lease of hazardous chemicals by 33% by
the end of 1992 and by 50% by the end of
1995.  One  objective of the EPA 33/50
Program is to evaluate, in a typical work-
place environment, examples of prototype
or innovative commercial technologies that
have potential for  pollution prevention.
Support for this  program also was  pro-
vided by the Connecticut Hazardous Waste
Management Service (CHWMS). The goal
of this study was to evaluate the techni-
cal,  pollution prevention,  and  economic
issues involved in using a recovery sys-
tem to recover the  rinsewater from the
chromating line in a metal finishing plant.
Chromium is a hazardous metal targeted
for early reduction under the EPA's 33/50
Program. The recovery  unit tested was
manufactured and provided by Cellini Pu-
rification Systems, Inc.1 Similar units with
varying capabilities may be available from
other vendors.
  The site for the testing was QRD Co., a
medium-size  metal finishing plant, in
Thomaston, CT.  QRD has operated the
chromating line with the recovery system
for about 1 yr. The recovery system con-
figuration at QRD is shown in Figure!
QRD uses three different chromate for-
mulations  blue, clear, and yellow  on
the chromating line.  The chromating line
receives a variety of parts (from QRD's
customers) that first are zinc-plated and
then chromated.
  Contamination  accumulates  mainly in
the Rinse  1 Tank, which functions as a
 Mention of trade names or commercial products does
 not constitute endorsement or recommendation for
 use.

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                         From
                    Zn Electroplating


                    From Mechanical
                       Zn Plating
                                 Still
                               Bottoms
Rinse 1    Rinse 2
                                                                          "Ciear'A \Water
                                                                         Chromate
                                                                           Tank
                                                                                     Purge Water |
                                                                                      Recapture  i
                                                                                 Sump \---*--'
                                                                                 Tank
                                                                    Cooling   \ 500 gal
                                                                     Tower
                                            Sample
                                             Port
                                                                               Water Recycle Line
Figure 1. Chromating rinsewater recovery system. (Sampling locations marked by an asterisk.)

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dragout rinse. This contaminated water is
processed through the recovery unit at an
average  rate of 1 gal/min.  The water is
first drawn into the recovery unit still. The
contents of the still are recirculated through
a  steam heat  exchanger  and  a  spray
nozzle back into the column  of the still.
The  water  is heated to  110F before it
goes through the spray nozzle and is flash-
distilled under vacuum.  In the column, the
down-flowing  liquid returns to the bottom
of the still  and the distillate vapor rises
upward and is later condensed by a wa-
ter-cooled condenser. The condensate is
stored in a small side tank, from which it
is  returned  periodically  by level control to
the Rinse 2 Tank,  which is the clean, final
rinse. The recovery system is  fully auto-
mated and  integrated into the chromating
line and requires very little operator atten-
tion.
  The chromating line operates for 1 shift/
day,   but the recovery  unit remains  on
24 hr/day so that the rinsewater gets ad-
ditional cleaning after the contaminant con-
tribution  from the chromating  line  stops.
Approximately 50  gal/day of fresh tap wa-
ter is  added into  the  Rinse  2  Tank to
make up for evaporative losses. Once ev-
ery 3 or 4 wk, the  still bottoms are evacu-
ated  into the  sump tank. The sump tank
also  stores the rinsate generated when
the chromate lines are purged before a
formulation switch. When the sump tank
is full,  QRD plans to  process its contents
through the recovery  unit and concentrate
it down to around  55 gal. This 55 gal of
concentrate containing  chromates can  be
either  reused or disposed of as hazard-
ous  waste. QRD  does not reuse  it  be-
cause it contains a mixture of three differ-
ent chromate  formulations. Other  plants
that use only a single formulation may be
able to reuse the concentrate.
  Testing  was conducted over one shift
(6 hr of continuous chromating line opera-
tion) and on the following morning before
the next day's shift. Samples were  col-
lected  periodically from the  locations
shown by  asterisks in Figure 1.

Product Quality Evaluation
  Rinsewater quality  was  monitored
throughout the shift,  and the results are
shown in  Table 1. Water quality in  Rinse
1 continues to  deteriorate as the contribu-
tion from the dragout increases. Contami-
nation in the Rinse 2 Tank is maintained
at very low levels  by the periodic influx of
clean processed water from the recovery
unit. As  the Rinse 2 Tank gets full, some
water is transferred manually into Rinse 1
to simulate a countercurrent flow through
the rinses. Overnight processing, while the
chromating line is not operating, helps to
reduce contamination further, as observed
in the 8:00 a.m. sample collected the next
morning.   Plants  that  operate  the
chromating line three shifts per day will
not have the benefit of this additional over-
night processing,  and contaminants may
accumulate to  levels slightly higher than
those shown for Rinse 2 in Table  1, until
an equilibrium  state is reached.
  Processed water coming out  of the re-
covery unit (before it reaches the Rinse 2
Tank) was also sampled and  analyzed
(Table 2). A tap water sample was  col-
lected and analyzed for comparison. The
recovery  unit  reduced  contamination of
chromium and zinc in the processed wa-
ter to levels slightly  above levels  in the
fresh (tap) water supply. Because tap wa-
ter at QRD normally is high in dissolved
solids,  the recovery unit was able to re-
duce the total dissolved solids (TDS) level
to below that  in the  tap  water.  Small
amounts of acidic components in the chro-
mate solution transfer over  into the distil-
late  as  seen  from the  low pH  of the
processed water. This,  in turn, progres-
sively reduces the pH in the Rinse 2 Tank
(Table  1). The low pH is not a concern in
this operation.
  Table  3 shows the characterization of
the  still bottoms and the chromate  solu-
tions. The contaminants that are removed
from the rinsewater can be  noticed accu-
mulating in the still  bottoms.  From this
table, it can be seen that if the still  bot-
toms materials is concentrated further, the
chromate concentrations would ultimately
reach those in the chromate tanks.  If only
one formulation were being used, the final
concentrate could have been returned to
the  chromate tanks.  Zinc and dissolved
solids levels in the  still bottoms are still
relatively low to be of concern during re-
use.

Pollution Prevention Evaluation
  Without the  recovery system, QRD
would  maintain  a  continuous  5 gal/min
flow of fresh water to Rinse 2 (clean final
rinse). The overspray in Rinse 2 would be
collected and sprayed in Rinse 1 (dragout).
After Rinse 1, the water would be taken to
the  on-site wastewater treatment plant.
For one 6-hr shift/day, 5 days/wk,  50 wk/
yr operation,  450,000 gal of wastewater
Table 1. Water Quality in Rinse Tanks
Sample No.
Rinse 1 Tank
W-R1-1
W-R1-2
W-R1-3
W-R1-4
W-R1-5
W-R1-6
Rinse 2 Tank
W-R2-1
W-R2-2
W-R2-3
W-R2-4
W-R2-5
W-R2-6
Time

9:30 a.m.
11:00 a.m.
12:30 p.m.
2:00 p.m.
3:30 p.m.
8:00 a.m.?

9:30 a.m.
11:00 a.m.
12:30 p.m.
2:00 p.m.
3:30 p.m.
8:00 a.m.?
Cr
mg/L

2.57
12.0
29.5
14.6
24.7
8.91

0.21
0.435
0.589
0.843
1.35
0.593
Zn
mg/L

4.5
23.5
61.0
32.5
53.2
26.1

0.4
1.15
1.50
3.28
3.97
2.42
TDS*
mg/L

48
162
372
273
374
196

42220
174
141
119
88
28
Cond.
nmhos/cm

60
200
475
340
450
312


190
180
160
130
55
pH

4.39
4.20
4.08
4.30
4.14
4.46

280 6.47
7.11
6.85
5.22
4.56
3.90
* Total dissolved solids.
 Next day.

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Table 2. Processed Water Quality
Sample No.
W-PW-1
W-PW-2
W-PW-3
W-PW-4
W-PW-5
W-TW-lt
Time
9:30 a.m.
11:00 a.m.
12:30 p.m.
2:00 p.m.
3:30 p.m.
12:30 p.m.
Cr
mg/L
0.235
0.348
0.437
0.445
0.482
0.079
Zn
mg/L
0.338
0.592
0.793
0.796
0.870
0.291
TDS*
mg/L
30
32
42
31
9
250
Cond.
^mhos/cm
55
60
80
80
80
400
pH
3.88
3.76
3.63
3.68
3.71
6.39
* Total dissolved solids.
 Field blank consisting of tap water supply at QRD.
Table 3. Characterization of Distillation Still Bottoms and Chromate Tanks
Sample No.
Still Bottoms
C-SB-1
C-SB-2
C-SB-3
C-SB-4
Chromate Tanks
Blue
Yellow
Clear
Time

9:30 a.m.
12:30 p.m.
3:30 p.m.
8:00 a.m.?

2:00 p.m.
2:00 p.m.
2:00 p.m.
Cr
mg/L

162
168
216
224

1,254
1,471
3,860
Zn
mg/L

258
277
385
420

1,739
15
0.743
TDS*
mg/L

2,280
2,240
3,170
3,610

16,740
3,590
25,110
Cond.
^mhos/cm

2,700
2,500
3,200
4,000

12,000
15,000
28,000
pH

3.52
3.59
3.80
3.95

2.57
1.55
2.87
  Next day.
  Total dissolved solids.
(requiring treatment) would be generated
annually. Not  only would QRD  have to
accommodate  this new influx of wastewa-
ter; the sludge generated  in their treat-
ment plant would have to be handled  and
disposed of as hazardous waste because
of the  presence of chromium. By using
the recovery system, QRD not only saves
nearly 450,000 gal of water, but also  pre-
vents  the creation of  a  large, new,  haz-
ardous waste stream. Instead, it generates
only about four drums  of still bottoms con-
centrate that has to be disposed of. This
waste concentrate can be avoided through
reuse by plants that use only one formula-
tion. QRD adds approximately 50 gal of
fresh water to  the Rinse 2 Tank daily to
make up for  evaporative  losses in  the
system.
Economic Evaluation
  Table 4 lists the major costs of operat-
ing with and without the recovery system.
The  recovery unit provides a savings in
annual operating costs of $23,082. QRD's
recovery unit cost $78,000 with an addi-
tional $9,000 cost for installation and aux-
iliary  equipment (such  as  cooling tower,
piping, etc.). A payback period of 4 yrwas
estimated at QRD for the investment.

Conclusions
  The recovery system at  QRD prevents
the generation of large volumes  of waste-
water and  hazardous sludge that other-
wise  would result from the  chromating
operation.  Further pollution  prevention
would be possible at plants that use only
one  formulation, through potential  reuse
of the chromium contained in the still bot-
toms  concentrate.  Rinsewater quality is
maintained at acceptable levels through-
out the shift without adding large volumes
of fresh water. By eliminating wastewater
treatment costs, considerable savings are
realized at QRD that  result in  a reason-
able payback period.
  This system  has potential  for  use in
many applications  that  generate  waste-
water. One concern is the relatively high
energy (steam) consumption of the recov-
ery unit.  Future versions of this system
are focusing on reducing this energy re-
quirement.
  The full report was submitted  in fulfill-
ment of Contract No.  68-CO-0003, Work
Assignment No. 3-36, by Battelle  under
the sponsorship of the U.S. Environmen-
tal Protection Agency.

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Table 4. Major Operation Costs Comparison
Item
                                       Annual Amount
Without Recovery System
Water (rinse)

Wastewater treatment
 450,000 gal

 450,000 gal
With Recovery System
Water (rinse, makeup)
Water (cooling, makeup)

Waste disposal

Energy
   - electricity
   - steam

Maintenance

Labor
   12,500 gal
   12,500 gal

      55 gal
60,950 kW hr
 3,000,000 Ib
                                               100hr
                                     Unit Cost, $
                                Annual Cost, $
 4.65/1,000 gal

88.00/1,000 gal

       TOTAL

 4.65/1,000 gal
 4.65/1,000 gal

  350.00/55 gal
   0.068/kW hr
      0.004/lb
                                                                                 8.00/hr

                                                                                 TOTAL
 2,093

39,600

41,693

    58
    58

   350


 4,145
12,000

 1,200

   800

18,611

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 Arun R. Gavaskar, Robert F. Olfenbuttel, and Eric H. Drescher are with
   Battelle, Columbus, OH 43201.
 Lisa Brown is the EPA Project Officer (see  below).
 The complete report, entitled "Chromate Recovery from Chromating
     Rinsewaterin the Metal-Finishing Industry,"(OrderNo. PB95-243044;
     Cost: $17.50, subject to change) will be available only from:
         National Technical Information Service
         5285 Port Royal Road
         Springfield, VA22161
         Telephone: 703-487-4650
 The EPA Project Officer can be contacted at:
         National Risk Management Research Laboratory
         U.S. Environmental Protection Agency
         Cincinnati, OH 45268
United States
Environmental Protection Agency
National Risk Management Research Laboratory (G-72)
Cincinnati, OH 45268

Official Business
Penalty for Private Use
$300
     BULK RATE
POSTAGE & FEES PAID
         EPA
   PERMIT No. G-35
EPA/600/SR-95/087

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