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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