ENERGY AND MATERIALS RECOVERY OPTIONS
FOR THE TEXTILE INDUSTRY
Fran Kremer, Environmental Engineer
Barbara Broomfield, Environmental Engineer
Larry Fradkin. Environmental Engineer
Energy and Environmental Systems Division
Argonne National Laboratory
Argonne, Illinois 60439
Nearly half of the textile mills in the United States, excluding mills with low water use,
indirectly discharge their wastewater without further treatment; as a result, the organic
constituents of these streams pose significant problems for publicly owned treatment
works (POTW) and aquatic life. Those facilities that provide treatment generally use some
form of the activated sludge process. In most cases, this type of process can produce an
acceptable effluent, but it generates significant quantities of sludge. On a wet weight basis,
the textile industry is second only to the electroplating industry in its production of
sludge [ 1 ].
The organics discharged consist primarily of sizes, dyes and detergents. Treatment of
these constituents provides the basic treatment of any plant's scheme . In the future, however, more concern will need to be placed on the treatment of priority pollutants generated
by the industry.
DESCRIPTION OF POLLUTANTS AND
PROPOSED TREATMENT OPTIONS
Sizes
Sizes represent the single largest group of chemicals used in the industry. Starch has been
the traditional sizing material used in textile manufacturing, but mills have been increasing
the use of synthetic sizes polyvinyl alcohol (PVA) and sodium carboxymethylcellulose
(CMC) as a replacement for starch for use on synthetic and synthetic-blend materials.
Several forms of PVA, the most widely used synthetic sizing, are commercially available.
The biodegradability of PVA has been controversial: it contains an acetate substituent
group, as does starch and cellulose, to decrease rotting and decay. The degradation of PVA
is dependent, however, upon the stereochemical arrangement of the substituent groups
around the anomeric carbon atom [2] and on bacterial acclimiation. In starch and cellulose,
the number and location of acetate groups are different from those of PVA; consequently,
the degradation properties are different. Starch is readily biodegradable and its addition to
ananerobic digesters could enhance methane gas production.
The synthetic sizes are more expensive than starch; consequently recovery of these sizes
from wastewater could be more cost-efficient that degradation. Ultrafiltration (UF) of textile effluents offers the greatest promise for sizing recovery. Two modes of operation are
available: single pass and staged recirculation. In a single pass arrangement, influent is
maintained at high pressure and velocity. A porous stainless steel tube is coated on the
inner surface with an inorganic membrane, zirconium oxide. The steel construction allows a
high operating pressure (1000 psi) and the membrane material allows a high operating
temperature (212°F) [31. A multiple-stage process requires less area of membrane to concentrate the same volume of solution than does a single pass operation. Three types of
modules are available: spiral wound, hollow fiber and low pressure tubular units.
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