United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S2-85/139 Jan. 1986
&EPA Project Summary
Hyperfiltration for Textile
Preparation Caustic Discharge
Reduction
Craig A. Brandon
Hyperfiltration (HF) is a membrane
separation technique widely used in
desalination of natural water and in
some industrial separation applications.
Because energy, process chemicals, and
water are discharged from industrial
processes in large quantities, recycle
has been studied with the objectives of
energy and material conservation and
pollution abatement. The results of
several research projects with formed-
in-place membranes are the background
for the current project, which is the
joining of an HF system with an oper-
ating caustic scour and preparation
range in an integrated textile dye and
finishing plant. The effluent treated by
HF is a 3 to 10 weight percent caustic
(NaOH) solution. The caustic percent-
age and the amounts and types of
contaminants in the effluent depend on
the style and weight of fabric being
processed.
HF membranes formed on porous
sintered-steel tubular supports are used
to remove contaminants from a hot
(95°C) caustic scour solution and render
it reusable for scouring. For this demon-
stration over 15 million m of approxi-
mately 1.5 m wide fabric was scoured
using over 3 million L of recycled caustic
solution. The initial prototype unit was
replaced with an improved design, using
316L stainless steel porous material to
achieve the necessary corrosion resist-
ance.
Results of this prototype project indi-
cated a positive rate of return with
savings estimated at $379,900/yr,
greatly exceeding the installed capital
($361,500) and operating ($37.9007
yr) costs. The prototype unit is being
expanded from 100 to 210 m2, and a
second 220 m2 HF unit is also being
installed.
The report describes the applicable
textile process, the reuse scenario, and
the HF unit and its operation.
This Project Summary was developed
by EPA's Air and Energy Engineering
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 infor-
mation at back).
Introduction
The technical feasibility of using formed-
in-place hyperfiltration (HF) membranes
to renovate a variety of textile waste-
waters for direct recycle was shown in a
series of research projects conducted as '
part of a cooperative program between
the textile industry and the U.S. EPA,
beginning in 1972. The current project
demonstrates the use of an HF unit to
recycle 3 to 10 weight percent caustic
(NaOH) at 95°C from a cotton scour
saturator. This project was funded by a
cooperative agreement between the EPA
and CARRE, Inc. The Graniteville Com-
pany, Graniteville, SC, provided the cap-
ital equipment and evaluated the produc-
tion procedures used during testing.
The wide scale implementation of HF to
recycle caustic process effluents would
have a large impact on pollution abate-
ment. The cost of achieving this pollution
abatement with HF would be offset by the
combination of savings from the simul-
taneous recovery of energy and caustic
solution. In addition, the subsequent
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waste treatment of the concentrated
contaminants may be improved because
of the reduced volume of the waste
stream.
Hyperfiltration
Hyperfiltration is a fluid separation
process utilizing a semi-permeable mem-
brane. Permeation through the mem-
brane is driven by pressure differential.
Since the separation is achieved without
a change of phase, membrane separation
is inherently more energy efficient than
processes involving a phase change; e.g.,
evaporation or freezing. The optimized
single-pass arrangement, which requires
no recirculation of any concentrated
material, utilizes about 10 BtuVkg of
solvent passing through the membrane,
or about 30 Btu/kg of solvent separated.
Change-of-phasetechnologies(e.g., freez-
ing and evaporation) require 4 to40 times
as much energy per kilogram of solvent
separated.
Initial interest in membrane separation
was largely directed to desalination of sea
and brackish water. Attempts to utilize
the technology in industrial situations
encountered restrictions due to the in-
ability of commercially available equip-
ment to tolerate the high temperature
and corrosive composition of the typical
industrial waste streams. The innovation
of zirconium oxide/polyacrylic acid
(ZOPA) membranes (formed in place on
sintered stainless steel tubes) relaxed
many of the limitations. ZOPA mem-
branes were utilized in the prototype HF
system studied in this project.
Textile Caustic Recovery
Caustic solutions are used to clean
equipment and products in many indus-
tries. A survey of chemicals used in the
textile industry in 1977 estimates that 1
million kg of caustic was discharged from
cotton preparation processes Much ad-
ditional caustic was used and recovered
by evaporation. The discharged caustic is
normally neutralized with acid addition
and discharged to a municipal waste
treatment plant.
The objective of this project was to
demonstrate the use of hyperfiltration to
recover the caustic overflow from a scour
saturator. The overflow is too dirty for
reclamation by existing evaporators.
The scope of this project included both
the operation of an HF recovery system
coupled with a full scale cotton scour
saturator and the determination of oper-
ating costs and technical feasibility of the
system as a means of reducing caustic
discharge from fabric preparation.
Project Results
For 2 years HF membranes were oper-
ated with the overflow caustic (6 to 10
weight percent NaOH) at 95°C from a
scour saturator in a cotton preparation
range. During this time, the caustic
discharge from this plant was reduced by
about 200,000 kg of NaOH.
After initial operation of a pilot plant (10
m2 of membrane), a prototype unit (100
m2) was installed. The prototype unit
experienced corrosive problems in the
sintered metal membrane support. A
properly prepared 316L grade stainless
steel module (7.2 m2) was installed and
operated successfully for over a year. The
entire 100 m2 prototype system was then
replaced with modules made of the new
material.
The technical feasibility of reuse of the
caustic was proven by the production of
over 15 million m of approximately 1.5 m
wide fabric while recycling over 3 million
L of renovated 6 to 10 weight percent
caustic (NaOH).
Operating procedures were also devel-
oped. Daily washing was established,
involving a base-solvent solution for
removing organics and an acid solution
for removing metallic oxides and hydrox-
ides.
A routine procedure for completely
stripping and reforming membranes in
place was also established. Details of the
membrane formation-in-place procedure
are proprietary.
Operating costs, including labor and
chemicals for cleaning and a technology
support contract that provides the time
and materials for membrane formation-
m-place, were established. The savings
of $379,900/yr yield a positive rate of
return on the $361,500 installed cost.
Annual operating costs are $37,900.
These results led to an expansion to
over 200 m2 of membrane area that is
scheduled to begin operation in late 1985.
(Also, anHF unit of about 220m2 is being
installed to renovate mercerizer wash
water, 6 weight percent NaOH, for use as
dyehouse reagent.)
*1 Btu = 1 055 kj
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C. A. Brandon is with CARRE, Inc., Seneca, SC 29679,
John S. Ruppersberger is the EPA Project Officer fsee below}.
The complete report, entitled "Hyperfiltration for Textile Preparation Caustic
Discharge Reduction," (Order No. PB 86-134 053/AS; Cost: $9.95, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, V'A 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park. NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use S300
EPA/600/S2-85/139
0000329 PS
U S ENVIR PROTECTION ACEMCY
RE6ION 5 LlftRARY
SO S OEARSORN STREET
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