Reclamation of Textile Printing
Wastewaters for Direct Recycle
WAYNE M. KACHEL, Graduate Student
THOMAS M. KEINATH, Associate Professor
Department of Environmental Systems Engineering
Clemson University
Clemson, South Carolina
INTRODUCTION
The textile industry in the United States has experienced much change during the past
decade, not only in the type of cloth being woven, but also in the types of processes and
process chemicals employed. Weaving of traditional cotton fabrics has been displaced
largely by synthetic and blended fabrics due to unprecedented consumer demand for such
goods. Technological innovations required for the production of these new fabrics have
resulted in changes in practically every facet of the textile industry, with new process
chemicals being introduced that are suitable for use with the synthetic fibers.
Production of woven blended textile goods generally involves slashing, weaving,
desizing, scouring, bleaching, dyeing, and finishing operations. The finishing process itself
may consist of several distinctly different operations including printing and the application
of permanent press or fire retardant finishes to the cloth. Although colored wastes emanate
from both the dyeing and printing operations, those discharged from the printing process
contribute the majority of colored materials to the wastewater when both dyeing and
printing processes are employed.
In printing operations colored designs are placed onto the fabric by transferring
printing pastes to the cloth by either a roller or panel process. The highly colored
wastewaters that are discharged from the printing equipment result entirely from rinsing
excess printing pastes from the unit. These pastes contain printing pigments, adhesives, an
acrylic latex emulsion, and a suitable solvent, commonly varsol. Consequently, the
wastewaters discharged from printing operations contain predominantly these materials of
which the printing pigments are clearly particulate or colloidal in character.
Characteristically, printing wastewaters have a highly variable chemical composition.
It has been shown in a previous study (1) that although the chemical oxygen demand (COD)
for a 24-hour composite sample was 6020 mg/1, the values of COD ranged from a minimum
of 117 to 18,080 mg/l for samples collected on two-hour intervals during a one-week
period. Similarly, solids determinations on the same discrete samples showed ranges of 5 to
2700 mg/1 and 156 to 3340 mg/1 for suspended and total dissolved solids, respectively. The
pH and total (methyl orange) alkalinity, conversely, were found to be relatively constant
averaging 8.1 and 58 mg/l, respectively.
Treatment of textile wastewaters has heretofore been accomplished by use of one of the
biological treatment processes, most commonly by aerobic or anaerobic lagoons. Because
most of the chemicals employed in the printing operation are relatively resistant to
biological oxidation and because the printing pigments themselves are particulate and are
not readily solubilized by microorganisms, biological degradation of printing wastewaters
has had limited success in the past. In fact, removals of the colored pigment materials by
biological methods have rarely exceeded the 20 to 30 percent level-which certainly is
unacceptable in light of today's stringent water quality standards.
Due to the fact that printing wastewaters are predominantly particulate or colloidal in
character, it would appear that this wastestream could effectively be renovated by particle
destabilization, aggregation, and subsequent solids/liquid separation through the use of
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