United States
                   Environmental Protection
                   Agency          	
Risk Reduction Engineering
Laboratory
Cincinnati OH 45268
                   Research and Development
 EPA/600/S2-89/052  Dec. 1989
&EPA         Project  Summary
                   Assessing  Chemical  Releases
                   and  Worker  Exposures from  a
                   Filter  Press

                   James Scott, Keith Sherban, and Mary Marshall
                    Chemical releases and  worker
                  exposures associated  with  the
                  filtration of an industrial wastewater
                  sludge were characterized. The filter
                  was a recessed chamber filter press
                  with an  open filtrate  discharge
                  system.  Chemical  releases  and
                  worker exposures for a selected
                  chemical were  measured over  four
                  operational  cycles and various
                  aspects of the filtration operation
                  believed  to   influence   the
                  measurement   values   were
                  documented. The filter  press  and
                  ancillary systems  are described as a
                  reference for the  measured releases
                  and exposures. Bulk samples of the
                  feed stream,  filter cake,  and filtrate
                  effluent were taken together  with the
                  mass  quantities for the  batch
                  filtration cycles to further define the
                  operational conditions.  The three
                  sequential  stage  activities
                  comprising each  filtration operation
                  are described  along with  worker
                  exposures and durations for each
                  stage. Ventilation patterns around the
                  filter press were monitored.
                    The worker's  time-weighted aver-
                  age exposures to total copper (low
                  vapor  pressure,  highly  insoluble
                  form)  during  the  113-minute opera-
                  tional  cycle ranged from 3.1 to 25
                  u.g/m3. The sludge feed  and filter
                  cake copper concentrations  were
                  approximately 0.1 and 1.0 weight per-
                  cent.  A noticeable  difference in
                  worker techniques was  observed
                  which  may account for  the large
                  range  of inhalation exposures during
                  the cake removal  stage. During this
                  stage,  the inhalation exposures
                  ranged from 11  jig/mS to 130 jig/m3.
The manual removal of filter cake
comprised only 15% of the time in an
average filtration cycle, but produced
72% of the  worker's  inhalation
exposure.
  This  Project  Summary was
developed by EPA's Risk  Reduction
Engineering 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).
Introduction
  For the study  summarized herein,
inhalation and dermal worker exposures
as well  as  chemical releases were
characterized   at  an  electronic
manufacturing plant. The parameters
(exposures and releases) were measured,
and the aspects of the operation believed
to influence these  parameters were
documented over  four filtration cycles.
Each cycle was  composed  of  three
stages: sludge filtering, filter cake drying,
and filter cake removal.
  This assessment study is part of a joint
research  effort undertaken by the  U.S.
Environmental Protection Agency and
Southwest Research Institute. The overall
goal of the cooperative agreement  is to
develop  database models for use  in
predicting chemical releases and worker
exposures from  select  filtration  and
drying unit operations. The  database
models developed will be applicable for
the Premanufacture Notice (PMN) review
system.  For each study  the  chemical
monitored is a  surrogate  for  a
hypothetical PMN new chemical in order
to evaluate  the worker exposures and

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chemical  releases  from  the  unit
operation. Thus, there is no requirement
to select an operation which has a toxic
chemical, provided  that  the  physical
properties of the chemical  can  be
extrapolated to the  hypothetical  PMN
new chemical. The surrogate chemical at
Plant 50 is total copper.
  The  sludge was from  a metal  rinse
stream.  Because  the metal  with the
highest concentration  was copper, total
copper (both soluble and insoluble) was
selected  to evaluate  worker exposures
and chemical releases.
  For each unit operation  cycle, sludge
was  pumped  from a  storage tank to a
recessed chamber  filter press. In the
sludge filtering  stage, the  solids  (filter
cake) were collected  in the chambers of
the press while filtrate exited the  press
through spigots on the side of each plate
into an open collection trough. The filtrate
further drained into a sump and was then
pumped to an effluent storage tank. This
process continued until the press was
(approximately) filled with cake.
  Once the press was  filled, the cake was
blown with compressed air (the filter cake
drying stage). The air entered the  press
through the same port as the sludge and
exited the  press through the  same
spigots as the  filtrate. The  discharging
compressed air  created  a mist in  the
vicinity of the press.
  After the drying stage, the filter cake
was removed. As  the  press was opened,
one  plate  at a  time, the  filter  cake
dropped  into  a collection hopper.  The
filter cake was transported with a screw
auger to a collection  trailer. Cleaning  the
last chamber of the press completed  the
filter cake removal stage.
  Two filter presses  were  housed in a
separate room  next  to  the main waste
treatment area.  The  recessed chamber
filter press used  in  this study had  23
plates (or 22 chambers), which were each
approximately 1  m in length and  width
and  4.5 cm thick. (The other press  did
not operate during this study.) The total
filtration surface  area  was 34.8  m2, and
the total filtration volume  was 0.70 m3.
The  overall size of the press was 5.0 m
long by  1.6 m wide by 2.3 m  tall. The
press was equipped with a hydraulic ram
closure mechanism  and  an automatic
plate shifting device.

Procedure
  All data were  categorized according to
the  three  filtration  stages mentioned
above. Worker exposures were assessed
during four  cycles  of  the  filtration
operation, and chemical   release
measurements were taken during the first
three cycles. The emissions from sealing
points were evaluated during  the sludge
filtering stage in the fourth cycle. For all
four  cycles, the  sludge came from a
single, isolated storage tank.
  Background,  area,  and  personnel air
samples  were  collected with  the use of
battery-operated pumps, duPont P4LCs*,
to pull air through 0.8 p mixed-cellulose,
ester  membrane filters. The background
air samples were collected  where air
either entered into or exited from the filter
press room.  Two area  samples  were
located  at the  ends  of  the filtration
collection  trough  and one  by a control
panel. The personnel sample collection
cassettes were  attached  to   each
operator's shirt collar.
  Wipe  samples  were  collected  on two
flat horizontal  areas  of the  filter  press,
one at each end of the filter press.
  In  conjunction with  measuring the
volumes  of sludge feed  and filtrate, as
well as weighing  a chamber of the filter
cake,  bulk samples  were taken of  the
sludge feed, filtrate, and filter cake The
sludge feed samples were grabbed from
the storage tank immediately before the
start of  the sludge filtering stage. The
filtrate samples were  collected at  the
outlet of  the collection  trough discharge
pipe.  Small fragments of filter cake were
selected from  the chamber  that  was
weighed.
  Copper analyses of  the  sludge,  filter
cake,  wipe,  and  filtrate  samples  were
done  by direct  aspiration flame atomic
absorption spectrophotometry, employing
Method  220.1  of Methods  for Chemical
Analyses  of Water  and Wastes  (EPA
600/4-79/020).  Method 160.3 of the  same
reference was used to analyze   total
residue. NIOSH  Method 7029 was used
to analyze the air samples for copper,
except  that graphite  furnace  atomic
absorption spectrophotometry  was  used
for greater sensitivity.
    A Kurz  441  M  Air Velocity  Meter
measured air  velocities. Smoke  tubes
indicated gross air movement within the
filter press room.

Results
  Worker inhalation  exposure measure-
ments  for  airborne copper   were
performed for  four  filtration  operation
cycles using three operators, A-1, B-1,
and  C-1  [the  first  operator  (A-1) was
monitored twice]. The  geometric  mean
exposure, the average  duration of the
 'Use of trade names or commercial products does
 not constitute endorsement or recommendation
 for use
stage,  and the average  duration of
operator's involvement during each si
as well as the entire unit operation
summarized in Table 1  (the  minimi
and maximums are also  presented).
total copper concentrations in the slu
feed  and the  filter cake  w
approximately  0.1% and 1.0%  by wei
respectively. Total copper was in a hi'
insoluble form  with a low vapor pressi
  The  head, neck, and  lower  arm a
comprised the exposed  skin surfaces
all of the operators. Since  the sec
operator (B-1) did not wear any gl<
(and operators A-1  and C-1  did),
hands were also potential sites for de
exposure. The routes by which  co|
was deposited on the skin were airb
aerosols and contact with surfaces (w
had visible deposits of green dust) ir
filter press room.
  The  air  and wipe sampling res
indicate  the  airborne  copper con'
trations  made aerosol  deposition
exposed  skin surfaces a  neglig
consideration.  Deliberate  contact
surfaces occurred when the  oper<
opened and closed valves, turned on
off pumps, grabbed the outer  edge
some of the plates and slid them slii
forward to ensure  they  were  corn
aligned  with   the  filter  cloths,
occasionally held onto  the  side  of
press for  support while  peering intc
press to inspect the filter cloths for
residue. Incidental contact occurred \
the operators  hit  their lower arms
hands  for operator B-1)  on  vai
surfaces.
  No direct  contact with the  slu
filtrate, or filter cake was observed.
  The  ventilation measurements sh<
that air movement through the filter |
room was relatively  constant at a i
location throughout the study,  but tr
velocities varied from location to loci
Smoke tube studies  showed most  c
air that entered the room via the
doorway flowed directly towards the
doorway. (These doorways were lo<
towards the front of the room on the
wall. There were  no other entrance
the air, except through leaks in the v\
the lower level, and only one  other
the south wall exhaust  fan.) As th
moved  from east to west, very litt
from the work area by the filter pn
became entrained  into this  mai
current. The  operators,  however.
most of their time in the other  porti
the  room  where  the  filter  press
located  and  in  which  ventil
stagnation occurred.
  An overall mass balance approach
appropriate  samples  taken  for

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Table 1. Operators' Geometric Mean Inhalation Exposure to Airborne Copper
        Duration of the Stages and Operators' Involvement
Stage
Sludge Filtering
Cake Drying
Cake Removal
Entire Operation (TWA)
Geometric
Mean
Exposure,
fig/m3
4.1
1.6
30
6.4
Minimum
Exposure,
}ig/m3
3.8
0.8
11
3.1
Maximum
Exposure,
fig/m3
4.8
2.6
130
25
Average
Stage
Operation
Duration,
min
39
57
17
113
Minimum
Duration,
min
26
49
15
98
Maximum
Duration,
min
57
64
20
141
Average
Duration of
Operator
Involvement,
min
11
3
17
31
Minimum
Duration,
min
9
3
15
27
Maximum
Duration,
min
13
3
20
33
Table 2. Mass Balance Results
         Sample Site
      Mass Total, Kg
Mass of Total Copper, Kg
 Influent
     Sludge feed
Cycle 1  Cycle 2 Cycle 3       Cycle 1  Cycle 2 Cycle 3
 2150    1570    1660         2.9      2.0      1.9
Effluent
Filtrate
Filter cake
Total Effluent

1720
338
2058

1210
335
1545

1120
339
1459

0.001
5.3
5.3

0.001
3.0
3.0

0.0009
2.1
2.1
copper, was used to quantitate chemical
releases. Table 2 summarizes the results
(for the three filtration operational cycles).
  Although  the   average  percent
difference between  the overall  effluent
and influent masses was -6.3% (range of
-1 6%  to  13% with a sample standard
deviation of  5.9%),  the average  percent
difference  between  the  total  copper
masses in the  effluent and influent was
+ 36%  (range  of 10% to  59%  with a
sample standard deviation of 24%).
  In addition to the overall mass  balance
approach, spills and leaks were observed
and documented. These leaks and  spills
represent  releases  that would not  have
been  included  in  the  other  mass
measurements. The five  releases
observed were:  (1)  the air valve to  the
press leaked  1 drop of sludge onto  the
floor (of the  lower  level)  every  10 sec
during  the sludge filtering stage, (2)  the
recessed chamber plates  dripped  liquid
into the cake hopper;  six  leaks flowed at
a rate of 1 drop every 2 sec, (3) the  valve
to the sludge  feed  pump  leaked sludge
onto the floor  at a rate of 1 drop every
minute,  (4) the fine mist generated during
the  cake  drying stage from  the filtrate
spigots  fell onto the floor (of the  lower
level),  which  dampened  an area  of
approximately  1.5 m2, and  (5) the  small
fragments of  filter cake that missed  the
hopper  fell onto the floor (of the  lower
level) as the  recessed chambers  were
emptied during the  cake  removal stage;
the fragments of cake  averaged 5 cm3 in
volume.  It should  be noted that the
^ludge  dripping  from  the  leaks  in
  jmbers  1  through  3 was  somewhat
              clearer in appearance compared with the
              murky,  green  color of  the  sludge.
              Therefore, the  residue  and  copper
              concentrations in these leaks may have
              been  lower than those  in  the original
              sludge. During each filtration cycle, these
              spills  and leaks  released approximately
              1.1  g  of  total copper. The  total copper
              released  in  the filtrate  waste stream
              averaged  1  g per filtration  cycle. An
              estimated  23  mg of copper was present
              in the air exhausted from the  filter press
              room  during each  filtration  cycle.
              Consequently, the total chemical releases
              from  each  filtration  operation  was
              approximately 2.1 g of copper, or slightly
              less than 0.1% of  the total copper
              processed through the filter press.
                The  sealing  point evaluation  was
              performed to  measure  the  aerosol
              concentration generated by the operation.
              No  aerosol was detected above the total
              background levels (0.05 mg/m3) at any of
              the pumps,  valves,  or connections.
              Aerosol was detected at the 23  open-
              ended spigot  lines  and  the filtrate
              collection   trough.   The   aerosol
              concentration  detected  was 0.4 mg/m3.
              An  aerosol concentration of 1.0 mg/m3
              was also recorded for the  open-ended
              line discharging filtrate into  the  sump.  It
              must be  noted  that  the  measurements
              were for the total aerosol concentration;
              identification  of a particular species (e.g.,
              copper aerosol) was not possible.
              Discussion
                The  total  average duration  of  the
              filtration cycle was 113 min. Of this time,
                           the operator was actively involved in  the
                           operation for 31  min on  average  (or
                           27%).  If  an  operator  were  to  be
                           responsible for multiple filter presses,  the
                           "free  times"  within the various stages
                           could permit  the operator to stagger  the
                           stages  of  the  individual  presses  and
                           operate  them  simultaneously.  With
                           presses similar  to ones in  this study, an
                           operator could perform the  various tasks
                           on three presses and finish in a 147-min
                           period.  During  this span  of time,  the
                           operator  would  accrue a total exposure
                           duration of 93 min (three presses at 31
                           min each), which is equivalent to 63% of
                           the total time. Therefore, to determine  the
                           worker exposure during the total filtration
                           cycle, the number of filter  presses
                           operated by the worker must be known.
                             Based on a geometric mean inhalation
                           exposure, 72% of an operator's exposure
                           to copper  occurred  during the  cake
                           removal stage of the filtration operation.
                           Fifteen percent of an operator's time was
                           spent during  this  stage.  An  operator's
                           time weighted average (TWA) exposure,
                           based on the geometric mean, was  6.4
                           pg/m3.
                             To  determine an  operator's exposure,
                           the following formula could  be  used
                           (assuming the worker only operated one
                           press).
                                                          o
                                 HgTc _ ngTc (TWA)   1.25m
                                  day          3         hr
                                    hr of operation  # cycles
                                   x - x
cycle
                                                    day

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where Tc = target chemical.

For this study, the operator's exposure
would be  (assuming an  8 hr shift per
day),
                                g
    Hg copper  _ 6.4 pg copper  1.25 m

      day           3        hr
                   m
      (113/60) hr   4 cycles
     x	x —-—
        cycle      day
61 jig copper

   ~
  Observations  of the workers indicated
any dermal exposure incurred during the
sludge filter and filter cake drying stages
was  the  result  of  casual or incidental
contact of the hands  with contaminated
surfaces, which resulted in very minimal
exposure. The filter cake removal  stage
did provide a  greater  opportunity  for
dermal exposure since the workers were
in contact with the filter press and were in
proximity to the filter cake. No  direct
contact with the filter cake was observed,
however.
  The protective  equipment   each
operator  wore  included  chemical  safety
goggles at all  times  in the filter  press
room and  hearing  protection  devices
during the cake drying stage. Operators
A-1 and C-1 also wore cotton gloves.  In
addition, operator C-1  wore a disposable,
half-face dust respirator.
  Total copper  was  a  very small portion
of the material being processed.  As such,
the methods used to accomplish a mass
balance were too insensitive to accurately
or  precisely  quantitate the mass of total
copper.

Conclusions
  The workers' TWA  exposures to total
copper  over  the  113-min  average
duration of the unit operation  ranged from
3.1  to 25 u,g/m3.  The ACGIH's 1987-88
TLV for 8-hr exposures to copper dust
and mist is 1 mg/m3.
  The total copper concentrations in the
sludge feed and the filter  cake  were
approximately 0.1%  and 1.0% by weight,
respectively. Therefore,  it  is  uncertain
whether  the  low  worker  exposures
measured were solely attributed  to the
operational characteristics  of  the filter
press or were a reflection of the low total
copper concentrations.
  The area of the room most frequently
occupied  by  the  workers was  also the
area that received the least air circulation.
The  air flow rate and distribution pattern
inside the  filter  press room  remained
relatively constant throughout the study.
  Data from this research also indicate
that a worker's technique in removing the
filter cake  may be an important factor in
determining a worker's exposure to within
one  order  of  magnitude. The  range of
inhalation   exposures  during  the  cake
removal stage was  11  ng/m3  to  130
jig/m3. A noticeable difference  in worker
techniques was recorded for the high and
low exposure readings.
  The sludge filtering stage showed great
variability among the work paths taken by
the  filter   press operators  but  little
difference among  their  resultant
exposures (geometric mean exposure for
the four sludge filtering stages was 4.1
u.g/m3).  The  sludge  filtering  stage
comprised  roughly one-third of the 113
min  needed  to complete an  average
filtration cycle.
  The  filter cake drying  stage,  which
comprised slightly more than 50% of the
time for the filtration cycle,  was largely
unattended  by  the   operators  and,
therefore,  contributed  very  little  to their
exposures. The working time was 3 min,
and the geometric mean of the inhalation
exposures  to  airborne  copper  was 1 .6
                 Although manual removal of filter cake
               from the  chambers  of  the  filter press
               comprised only  15% of the  time in an
               average filtration cycle, it produced 72%
               of the workers'  exposures  to  copper
               during the filtration operation.
                 Dermal  exposures to total copper were
               not quantitated.  Observations  of the
               operators' work  practices indicated that
               their dermal  exposures  were probably
               very  low  and  effectively   eliminated
               through their use of  work  gloves  when
               removing the filter cake.
                 Total chemical  releases from the  filter
               press were estimated to be 2.1  g  of
               copper or 0.1% of the total copper mass
that  was  processed  through  the  u
operation. Although the mass of chemi
in  the filtrate  could  be  measured,  1
mass of chemical released in spills
leaks of the feed  material and filter Ce
could not be quantified. The study's d
indicate  that  leaks  or  spills of fe
material or filter cake can  be a gres
potential source  of  chemical  releas
than  from  the  total  filtrate effluent
insoluble filter cake products.
  Using a mass balance to calculate tc
copper processed through the filter pr<
was   not  an   effective  method
measuring the  individual   chemi<
releases. The  sampling  and  analyti
errors associated  with the mass balar
measurements  did not  permit  accur
calculations of  the  relatively sir
masses represented  by the  individ
chemical releases.

Recommendations
  The  in-plant  assessment study o
filter  press  unit operation  yielded d
that   provided  insight  into  worl
exposures  and chemical releases. Pi
scale experiments should be conduc
using different worker  scenarios  i
target chemicals  to  quantify  ranges
exposures  and chemical releases  t
can occur by varying these two variabl
  For a future  in-plant assessment sti
of a  filter press, any  one or more of
following criteria should be  consideret
the selection process-

• A liquid, high-molecular-weight, orge
  chemical should be studied.

•  An operation with a more concentre
  chemical  (cake product) in the fi
  stream should be used.

• A  larger  filter press (one  requiring
  operators to  remove  the filter a
  should be used.

  This report  was submitted  in  pa
fulfillment  of  Cooperative Agreem
CR813355 by  Southwest  Resea
Institute under the partial sponsorshii
the  U.S.  Environmental Proteci
Agency.

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James Scott, Keith  Sherban, and Mary Marshall  are  with Southwest Research
 Institute, San Antonio, TX 78284.
Dennis Tlmberlake is the EPA Project Officer (see below).
The  complete  report,  entitled "Assessing  Chemical  Releases and  Worker
 Exposures  from  a  Filter Press,"  (Order No. PB 90-119 587/AS; Cost: $23.00,
 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:
       Risk Reduction Engineering Laboratory
       U.S. Environmental Protection Agency
       Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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