United States
                    Environmental Protection
                    Agency
Industrial Environmental
Research Laboratory
Research Triangle Park NC 27711
                    Research and Development
EPA-600/S2-84-070 May 1984
v>EPA         Project  Summary
                     Wastewater  Recycle  and  Reuse
                     Potential for  Indirect  Discharge
                     Textile  Finishing  Mills
                    Jon F. Bergenthal
                      Over 80 percent of textile finishing
                    mills discharge their wastewater to
                    publicly owned treatment works. A
                    variety of wastewater recycle technolo-
                    gies have been developed to allow these
                    mills to reduce the volume of wastewa-
                    ter and amount of pollutants discharged.
                      Only a few of these technologies have
                    become widely  applied in the  textile
                    finishing industry. Specific technical
                    and economic factors affect the appli-
                    cation of most of these technologies at a
                    given mill; thus each application must
                    be  considered  under its  own mill-
                    specific conditions.
                      This report presents detailed informa-
                    tion on textile wastewater recycle/reuse
                    technologies. Included for each are a
                    description of  the  technology, its
                    environmental benefits, recycle system
                    and treatment  system  schematics,
                    design criteria, a discussion of technical
                    factors that limit or enhance its applica-
                    tion, capital and yearly cost, an exami-
                    nation of factors that affect  its eco-
                    nomic feasibility, lists of its current ap-
                    plications, and references for further in-
                    formation.
                      The information in this report is based
                    on a survey of the literature, discussions
                    with technology vendors and researchers,
                    and engineering  studies conducted at
                    six textile finishing mills. The six mill
                    engineering reports appear in Volume 2
                    of the report.

                      This Project Summary was developed
                    by EPA's  Industrial Environmental
                    Research Laboratory, Research Triangle
                    Park, NC, to announce key findings of
                    the  research project that is fully docu-
                    mented  in a separate report of  the
same title (see Project Report ordering
information at back).
Introduction
  About 4 million tons (3.6 x 109 kg) of
textile products are finished annually in
the U.S. About 2,000 finishing mills,
involved in this production, annually
discharge more than 100 billion gallons
(3.8 x 10" I) of wastewater. Most of the
water use and wastewater discharge in
the textile  industry is in four industry
sectors: (1) woven fabricf inishing, (2) knit
fabric and  hosiery finishing, (3) carpet
finishing, and (4) stock and yarn finishing.
  More than 1,000 textile finishing mills
were recently surveyed for the Effluent
Guidelines Division of EPA.  Survey
results  indicate that  81  percent of the
surveyed mills in these industry sectors
discharge their wastewater to  publicly
owned treatment works (POTW). The
amount of wastewater produced by these
indirect discharge  mills is estimated to
exceed 210 mgd. The survey  further
shows that much of this wastewater
receives either no treatment (58  percent
of mills) or only preliminary treatment (33
percent of  mills) prior to  discharge.
Preliminary treatment  includes: gross
solids removal by settling or screening,
equalization, and neutralization.
  Because of the significant total volume
of wastewater discharged to POTWs by
textile finishing mills, EPA's Office of
Research and Development, in support of
the Effluent Guidelines Division, is
evaluating textile mill wastewater recycle
and reuse  as  a way to reduce water
consumption and wastewater discharge
rates.

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  In addition to the benefits of reduced
water consumption  and wastewater
discharge, recycle and reuse can result in
significant  economic benefits to  an
indirect discharge textile finishing mill
from savings in water costs, sewer use
fees, end-of-pipe pretreatment costs,
energy, and chemicals. Therefore, signifi-
cant incentives for implementing waste-
water recycle and reuse exist even in the
absence of pretreatment regulations.
  Many textile manufacturing processes
have been identified in recent years as
being  suitable for the application of
wastewater recycle or reuse. Various
technologies have been investigated  for
these applications in tests ranging from
bench- to full-scale demonstrations.
Nevertheless, the application of recycle
and reuse  in textile finishing  mills
remains rather limited. Only a few recycle
technologies (e.g., caustic recovery from
mercerizing  washwater,  and direct  in-
process water reuse  by countercurrent
washing) have been adopted by a relatively
large number of mills. Most other recycle
technologies have been adopted by only a
few mills.
  Reasons for the limited use of recycle in
the textile finishing industry include:
   Lack of specific technical knowledge
     about available recycle/reuse tech-
     nologies, their benefits and limita-
     tions, and application of this infor-
     mation in performing a  feasibility
     study.
   Concerns about  the cost effective-
     ness of wastewater recycle (capital
     cost vs. return on investment).
   Competing areas for capital expen-
     ditures in the mill.
   Concerns about site-specific factors
     that could limit the applicability or
     cost effectiveness of recycle technol-
     ogies.
The goal  of this project,  providing
information  that defines the applicability
of recycle/reuse  in the textile finishing
industry,  is  achieved by performing  the
following tasks, grouped by project
phase.
Phase I
   1. Identify applicable recycle/reuse
     technologies and gather available
     information on them to define areas
     for  potential application, benefits,
     limitations,  and approximate  cost
     data.
   2. Identify a  group of textile finishing
     mills that appear to have high
     potential for applying recycle/reuse
     technologies.
  3.  Select six representative mills from
     this group to participate in actual
     field studies of the applicability of
     wastewater recycle/reuse measures
     under Phase II.

Phase II
  1.  Visit the six mills to collect informa-
     tion on textile processing, machinery,
     fiber and chemical use, energy and
     water use, and wastewater discharge
     and characteristics.
  2.  Technically evaluate the feasibility
     of employing various recycle/reuse
     technologies at the six mills, includ-
     ing bench-scale tests of the technol-
     ogies, when appropriate.
  3.  Economically  evaluate the  techni-
     cally feasible technologies to define
     capital costs, operating  costs, and
     textile production savings.

Phase III
  1.  Select one or more recycle technol-
     ogies that  have technical  and
     economic promise for more wide-
     spread use.
  2.  Develop these technologies to
     laboratory- and full-scale at a textile
     finishing mill.
  3.  Prepare a detailed manual covering
     the investigations  and application
     of the technologies.
  This report gives results of the first two
project phases. A separate report will be
issued, detailing the third phase.
Textile Finishing
  The major textile finishing processes,
in terms of wastewater generation, are
desizing, scouring, mercerizing, bleach-
ing, dyeing, and printing. Other operations
(e.g.,  applying functional finishes or latex
backing) generally result in only a small
quantity of wastewater.
  Desizing, performed only on woven
fabrics, is generally the first wet process
performed. It consists of removing sizing
compounds (e.g., starch, polyvinyl alcohol)
that were added to the warp yarns prior to
weaving.  Wastewater from desizing,
therefore,  contains high concentrations
of these organic substances.
  Scouring removes impurities from the
textile product prior to coloring and other
finishing processes. Wastewater from
scouring is generally alkaline and contains
the impurities removed from the product.
  Mercerizing, performed  on cotton
fibers, increases tensile strength, luster,
sheen, dye affinity, and abrasion resist-
ance.  The product  is contacted  for a
certain period with concentrated caustic.
and then is washed to remove residual
caustic from the fibers.
  Bleaching whitens cotton  and other
cellulosic fibers prior to coloring or other
finishing processes. Various oxidizing or
reducing compounds can  be used.
Exhausted  bleaching baths and rinsing
water are the sources of wastewater from
bleaching.
  Dyeing is a complicated  process that
imparts color to textile fibers. Various
dyestuffs are used depending on the fiber
type, color, and desired product specifica-
tions.  The  most  common classes of
dyestuffs include  acid, basic, direct,
disperse, vat, sulfur, and reactive dyes.
Various auxiliary chemicals are used in
the dyeing process including salts, acids
or bases for pH adjustment, reducing and
oxidizing chemicals, wetting agents,
sequestering  agents, retarding and
leveling agents, dispersants, and carriers.
Exhausted  dyebaths and rinsing water
are the sources of wastewater  from
dyeing.
  Printing   imparts color to  specific
selected areas of the fabric. Wastewater
results  from washing the fabric  after
printing and from equipment cleaning.

Technology Survey
  Many different types of recycle/reuse
technologies can potentially be applied to
the textile finishing operations just
discussed:
   Direct recycle/reuse (no treatment).
   Reconstitution and reuse.
   Separation and reuse by filtration.
   Separation and reuse by membrane
     separation processes.
   Separation and reuse by precipita-
     tion.
   Separation and reuse by evaporation.
   Separation and reuse by coagulation
     /flotation.
   Separation and reuse  by carbon or
     exchange resin adsorption.
   Chemical oxidation and reuse.

These technologies were  surveyed to
evaluate their applicability, technical and
economic feasibility, costs, and potential
for increased  use within the textile
industry. Equipment vendors and re-
searchers were contacted, the literature
was searched,  and engineering studies
were  conducted at six textile finishing
mills to evaluate these technologies.

Mill Studies
  Four woven fabric finishing mills, one
carpet mill, and one yarn mill participated
in the program's engineering studies.
  Mill  C-2  is a nylon  carpet  mill that
discharges 1 mgd wastewater, primarily

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from batch carpet dyeing. Various recycle
/reuse measures were investigated
including dyebath reconstitution, dye
wastewater treatment and recycle by
activated carbon or chlorine oxidation,
and cooling water use reduction.
  Mill W-3 prepares and finishes woven
fabric for apparel. Desizing, scouring,
mercerizing, bleaching, and printing are
performed and result in the discharge of
1.4  mgd  wastewater.  Size recovery,
caustic recovery,  recycle  of printing
wastewater, and cross-process reuse of
washwater were evaluated.
  Mill  W-4  discharges approximately
0.75 mgd wastewater from the weaving,
desizing, scouring, and piece dyeing of
woven polyester fabric. Reuse of water-
jet loom water, size recovery, and reuse of
dyeing wastewater by either reconstitution
or decoloring (chlorine oxidation) were
investigated.
  Mill  W-8  produces  woven industrial
fabric,  interlining, and pocket fabric.
Continuous ranges are used for preparing
and dyeing the fabric, and result in 0.4
mgd of process wastewater. Size recovery
and dyestuff recovery through membrane
separation processes, and countercurrent
reuse of washwater were evaluated.
  Mill  W-9 scours  and dyes woven
household fabrics.  Approximately 0.3
mgd of wastewater results  from these
operations. Hyperfiltration for dyestuff
recovery and water reuse on the contin-
uous dye ranges were investigated. Other
technologies studied included batch
bleach bath  and dyebath reconstitution,
and  reuse of  rinse  waters in batch
operations.
  Mill Y-4 discharges 0.8 mgd wastewa-
ter from the batch scouring, bleaching,
and  dyeing  of  yarn.  Reconstitution of
bleach baths and dyebaths was investi-
gated along with treatment and reuse of
dye wastewater by chlorine oxidation.

Results and  Conclusions
  Information developed on textile waste-
water  recycle/reuse technologies  is
summarized below.  In general, the
implementation of wastewater recycle/
reuse technologies is  very mill-specific.
As a result,  much evaluation, planning,
and testing must be performed to deter-
mine the applicability of any technology at
a given mill.


Dry and Low Water-Use
Processes
  Dry operations include weaving, knit-
ting, tufting, and spinning. No wastewater
results from these operations.
  Low water  use operations  include
slashing (sizing), latex backing, and
functional finishing.  Wastewater is
generated in  cleanup operations. Little
potential for  recycle/reuse exists with
these operations due to the small volume
of wastewater generated. Improved
housekeeping measures and better
cleanup practices are seen as the most
viable ways to reduce the wastewater
discharge from such operations.


Desizing
  Wastewater from  desizing contains
the sizing compound  that was applied to
the warp yarns prior to weaving. The goal
of recycle/reuse, as applied to desizing, is
to separate the sizing  compound from the
desize wastewater. The sizing compound
is then reused in slashing (sizing), and the
wash water is recycled to the  desizing
process.
  Size recovery and reuse is mandatory if
this recycle technology is to be economi-
cal. Thus, the fate of  the size during the
desizing operations is critical in deciding
if recycle/reuse can be  used. Starch
sizes, hydrolyzed during  removal, are
therefore not reusable. Most polyacrylic
and  polyester based  sizes are also
partially degraded in the  desizing step
and are not reuseable. Thus, recycle/re-
use technologies are  limited to sizes that
do not have to be degraded to be made
water soluble. These sizes  include
polyvinyl alcohol  (PVA), carboxymethyl-
cellulose (CMC),  and certain  modified
acrylic and polyester  sizes.
  Available technologies to separate and
recover size include thermal precipitation,
coagulation, evaporation, and ultrafiltra-
tion. Further use of these size recovery
technologies in the textile industry seems
to hinge on a few variables:
   Using thermal precipitation depends
     on whether sizing  compounds can
     be developed that offer weaving
     efficiencies comparable to currently
     popular sizing compounds.
    Using coagulation and evaporation
     is not seen as likely because of many
     unresolved technical problems, and
     the existence of a proven, alternative
     technology (ultrafMiration).
    The major obstacle to further  use of
     ultrafiltration for size recovery is the
     current practice  of slashing (yarn
     sizing) at  greige mills. Most large
     textile companies operate their own
     greige  mills and  can therefore
     control the type of sizing compounds
     used. The exclusive use of PVA or
     CMC sizing agents allows the sizing
     compound to be recovered. Also, a
     company-controlled greige mill is a
     ready outlet for the recovered PVA
     or  CMC size.  Some large textile
     companies have  therefore already
     instituted recycle systems for size
     recovery. The potential for expanded
     use of size recovery in these types of
     mills is  high. Payback periods are
     about 1 year.

     Many finishing  mills,  however,
     especially smaller companies and
     commission finishers, obtain their
     greige fabric from sources outside
     their own company. These finishing
     mills have little or no direct control
     over the types and variability of the
     sizing compounds on the fabrics
     received. This seriously hinders the
     feasibility of  adopting any  size
     recovery technology. In general,
     sizing at greige mills is  performed
     with  fast and efficient weaving as
     the prime consideration rather than
     the potential for  size recovery and
     reuse. The resultant mixtures of
     sizing compounds (especially  mix-
     tures of  starch and PVA which are
     prevalent on cotton-polyester blends)
     and variability in sizing formulations
     hinder both size removal at  the
     finishing mill as well as size recovery
     and wastewater reuse.
Scouring
  Wastewater from  cotton scouring
contains up to 2 percent sodium hydroxide
(caustic),  but  also  a  large  amount of
impurities. The caustic and  impurities
can be separated from the wastewater to
allow water reuse, with  technologies
such  as evaporation  or hyperfiltration.
But such recycle technologies cannot be
economically justified  on water savings
alone. Separation of the caustic from the
impurities to  allow  caustic recovery as
well as water reuse would be not only
difficult technically, but also very expen-
sive.
  Wastewater from  the scouring of
synthetic fibers contains little in the way
of valuable chemicals to be recovered, but
also contains much fewer impurities than
cotton scouring wastes. Therefore, reuse
of scouring wastewater (wash water) in
the desizing process, where water quality
requirements are less stringent, may be
technically feasible. Further application
of this technology must be on a mill-by-
mill basis after examining its feasibility.
  For all fiber types, the reuse of scouring
wash water in a countercurrent fashion
should be considered.

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Mercerizing
  Mercerizing wash water contains from
1 to  5  percent caustic along with a
relatively small amount of fabric impurities
and lint. The  goal of reuse/recycle with
regard to mercerizing  is to  recover a
concentrated  (30 to 40 percent) caustic
solution from the wash water for reuse,
and to recycle the treated wash water
back  to the  mercerizer washers, the
scouring washers, or the desize washers.
Again, the cross-process reuse of treated
wash water at the scour or desize washers
must be evaluated on a mill-by-mill basis.
Countercurrent flow is generally used in
the mercerizer washers to minimize the
flow of water to be treated.
  Evaporation is the traditional technology
used for caustic recovery at textile mills.
Payback periods  are  about 1  year.
However, many mills with large mercer-
izing  operations  have already installed
multiple effect evaporators  to recover
caustic. In addition, the amount of textile
products being mercerized has  been
steadily dropping due to the increased use
of synthetic  fibers. These two factors
indicate that only a  few  additional
applications for  Mercerizing caustic
recovery exist in the textile  industry at
present.

Bleaching
  Bleaching  wastewater contains un-
reacted bleaching chemicals along with
waste by-products of the  bleaching
operation. Reuse/recycle technologies
in this area include the countercurrent
use of  bleaching wash water,  cross-
process reuse of bleaching wash water in
scour or desize washers, and reconstitu-
tion of batch  bleach baths.
  Numerous  full-scale  applications of
countercurrent use of wash water exist.
Cross-process reuse of bleaching wash
water in the  scour of desize  washers is
less common and must be evaluated on
a case-by-case basis before implementa-
tion. For example, unexhausted bleach-
ing agents can react with and degrade
sizes  if  returned to the desize washers.
This  would  be  undesirable if  a size
recovery system were in place. However,
for many mills, the benefits of water and
energy savings, as well as the low capital
costs, suggest that more widespread
application of this technology can  be
expected.
  Bleach bath reconstitution is in rather
limited use.  More extensive use is
expected due to the benefits of water and
energy savings and low capital costs, but
this  may  be limited to synthetic fiber
bleaching. The bleaching of natural fibers
will likely result in too many impurities
in the bleach bath to allow for very many
cycles of reuse.

Dyeing
  Dyeing  wastewater contains unex-
hausted dyestuffs and auxiliary chemicals
used in dyeing. Several different types of
recycle-reuse technologies have been
developed for textile dyeing processes.
  Reconstitution  of  batch  dyebaths
utilizes the unexhausted auxiliary chem-
icals and dyestuffs in  the used dyebath.
Dyes, water, and  some  chemicals are
added  to  the used dyebath to permit
additional cycles of dyeing.
  Several other technologies  also utilize
the auxiliary chemicals remaining in the
dyebath, but remove or decolorize remain-
ing dyestuffs prior to water reuse. These
technologies include dyebath decoloring
by oxidation, activated  carbon adsorption,
or exchange resin adsorption.
  A third class of technologies attempts
to recover and concentrate unexhausted
dyestuffs from  continuous  dye range
wash water. Available technologies
include hyperfiltration,  ultrafiltration,
and coagulation/flotation of the residual
dyestuff. The treated wash water is often
reusable.
  In addition to these capital intensive
technologies that rely on dye or chemical
recovery and reuse to justify their
economics,  some less capital intensive
recycle  technologies  exist. Countercur-
rent washing can be used on continuous
dye ranges. In  batch  dyeing, the final
rinse water can  often  be  reused as
dyebath makeup water. In  the carpet
industry, water extracted from the carpet
after dyeing can also  be  reused  in the
dyeing  process. Cross-process  reuse of
dyeing  wastewaters  is generally not
feasible  if  any color or significant
amounts  of auxiliary dyeing chemicals
are  present. Further  details  on recycle
technologies for dyeing are given below.

Reconstitution
   Reconstitution has advanced from the
many laboratory-scale tests conducted in
the past several years to several full-scale
installations. While at first it was believed
that this recycle technology was limited
to  mills that performed much repeat
dyeing,  more recent experience has
shown that sequences of different colors
can readily be  scheduled into dyebath
reconstitution series.  A large number of
textile mills with batch dyeing operations
are thus candidates for adopting this
 recycle technology, even if only at a few
dye machines at a given  mill. Dyebath
 reconstitution requires  little capital
investment, and generally has a payback
period of less than 1 year.

Dyebath Decoloring
  Dyebath decoloring by oxidation  has
been instituted full-scale at several mills.
Chlorine is typically used as the oxidizing
agent, but ozone can also be used.  The
technology is limited to dyestuffs that are
amenable to decoloring. In general, acid,
basic,  direct,  and disperse dyes  are
treatable, though not all dyestuffs in each
class are treatable. More extensive use of
this technology can be expected  in the
future,  though  the economics are  not
particularly promising (payback period of
3 to 5 years).
  The economics of activated carbon
adsorption  for  dyebath decoloring  are
also not promising. Technically, most
soluble  dyestuffs can be adsorbed, and a
colorless  water produced for recycle.
Operating costs,  however, are usually
close to, or greater than, the cost savings
realized through water, chemical, energy,
and  sewer use  reduction.  Thus, no
incentive exists for more widespread  use.
Other less expensive adsorption technol-
ogies,  tested in  the  laboratory,  use
various  exchange  resins to absorb the
dyestuff molecules. Water recycle  has
not yet been demonstrated.


Membrane Separation
Processes
  Much laboratory and pilot-scale work
has been done with membrane separation
processes to recovery and reuse dyestuffs
from dye wastewater.  Most notable are
the use of hyperfiltration on continuous
dye range wash water, and the use of
ultrafiltration on wastewater from indigo
dyeing.  Hyperfiltration has been demon-
strated  as capable of producing a  high
quality water that can be recycled. For the
process to be economical, however, the
concentrated recovered dyestuff stream
must be reused. Full-scale testing at one
finishing mill is presently attempting to
resolve  problems in this area.
  Ultrafiltration of indigo dye wastewater
has been demonstrated, and full-scale
applications are now in place.  The
problem of dyestuff concentrate reuse is
very much simplified in this application
because only one dyestuff,  rather than
numerous  mixtures, is used in  dyeing.
Limited future applications of membrane
separation processes for dye wastewater
recycle  and reuse  are seen at mills with
large  quantities of single dyestuff  use,
such  as denim mills  (indigo dye)  and
industrial fabric mills.  More widespread
use will depend on whether the problems

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with mixed dyestuff concentrate reuse
can be resolved.

Coagulation
  An alternate technology for  dyestuff
recovery has been investigated. Vat and
sulfur dyes can  be coagulated  and
removed from  dye wastewater by the
dissolved air flotation process. One full-
scale application with indigo (vat) dye was
built in the 1970's. While limited reuse
was shown in the pilot-scale tests leading
to full-scale design, dye recovery was
never  totally demonstrated before the
mill  closed,  and  treated water recycle
proved too costly. Ultrafiltration appears
to be a proven alternative to coagulation/
flotation  in this application; therefore, no
future  applications of coagulation tech-
nology for dyestuff recovery are expected.

Other Technologies
  Numerous examples of countercurrent
use  of wash  water exist, and more
widespread use can be  expected due to
the benefits of water and energy savings
as well as the low capital cost involved.
  Reuse  of final  rinse  water for batch
dyebath  makeup has also been demon-
strated  at  many textile mills. More
widespread use of this technology is also
expected since it involves only procedural
changes  to attain the cost benefits of
water savings.

Printing
  Printing  wastes contain excess  pig-
ments, dyes, and solvents used in the
printing  process.  Equipment cleaning
water can be treated by coagulation/flo-
tation and filtration, if needed, to produce
a water that can be recycled for cleaning.
Solvents, if used, can be extracted from
the float and recovered for reuse. In some
cases,  cleaning water may require only
filtration  prior to direct reuse.
  In mills where soaping or washing of
the printed fabric is performed, counter-
current  flow  of washwater  can  be
instituted.  Cross-process use of soaper
water  in  other  processes,  such  as
backgray washing, may be feasible.
  Many  finishing mills with  printing
operations are primarily involved in
dyeing fabrics and perform only a limited
amount of printing. Institution of coagula-
tion/flotation facilities at these mills is
not considered to be cost effective. A
smaller number of finishing mills  have
extensive printing operations; many of
these have  coagulation/flotation facilities
in place but ony recover solvents or
pretreat their printing wastewater prior to
discharge.  Expanded  use  of  recycle of
wastewater at these  mills appears
promising. But the further expansion of
printwater recycle is not likely at printing
mills that currently have no coagulation/
flotation facilities, due to the high capital
costs  of the recycle technology and the
long payback period involved. Further use
of countercurrent flow on soapers can be
expected due to the low capital cost and
potential water and energy savings.
  J. F. Bergenthal is with Sverdrup and Parcel and Associates, Inc., St. Louis MO
     63101.
  Robert V. Hendriks is the EPA Project Officer (see below).
  The complete report consists of two volumes, entitled "Wastewater Recycle and
    Reuse Potential for Indirect Discharge Textile Finishing Plants:"
      "Volume 1. Technical Report," (Order No. PB 84-174 150; Cost: $19.00"
      "Volume2. Six Mill Engineering Reports," (Order No. PB84-174 168'Cosf
      $29.50"
  The above reports are available only from: (cost subject to change)
          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
          Research Triangle Park, NC 27711
                                                                  &U. S. GOVERNMENT PRINTING OFFICE: 1984/759-102/0937

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