77    CHARACTERIZATION AND BIOLOGICAL TREATABILITY
OF A TEXTILE DYEHOUSE WASTEWATER
Mervyn C. Goronszy,
Transenviro, Inc.
Irvine, California 92718
Harry Tomas,
Olympic Mills
Guaynabo, Puerto Rico 00651
INTRODUCTION
Olympic Mills is an integrated textile and apparel manufacturing company which produces T-shirts,
men's briefs, panties, etc; production typically operates over three shifts, 5'/2 days per week. Fabric is
knitted from 100% cotton or 50% polyester-cotton yarn, which is bleached and or dyed prior to
cutting, sewing and warehousing of the finished articles. Wastewaters are generated from bleaching,
dyeing, rinsing, boiler blow-down and water conditioning units. Woven cotton fabrics are bleached
(scoured) to generate a brilliant white product prior to direct dyeing procedures. Specific chemical
pretreatments are used in dyeing to remove starch based size preparations, to enhance dye absorbency
and to counter poor dye penetration due to fiber swelling. Chemicals are also used to increase dye
solubility and to improve dye affinity and its fixation. After treatments are used to remove the
unfixed dye portions. High concentrations of Glauber's salt or common salt, up to 140 g/L, are used
in cotton fabric dye liquors. The yield of color is improved in the case of deep dyeing at the high 140
g/L salt concentration, paler shades are obtained with salt concentrations down to around 6 g/L. Salt
additions are based on the mass of cotton fabric, the type of dye and the desired color. When dyeing a
polyester/cotton blend with reactive colors it is necessary to dye the polyester fraction first, in a two
bath procedure. The dye liquors from the polyester operation are dumped and the appropriate cotton
dye recipe followed. It is usual practice to scour the fabric blend. With direct colors, a one bath
procedure is used in which the polyester fraction is initially painted with the subsequent additions for
the cotton dye recipe without the intermediate rinsing stages that are used in the two bath procedures.
While Table I summarizes typical mass usage of major dye chemicals. The concentration of azo dyes
in the effluent stream from the dyehouse can be expected to be between 15 and 50 percent of initial
calculated values, depending on fiber type. While chloride concentrations in Table I are shown as a
mean daily concentration, actual dump load concentrations from a dye machine can be up to the
equivalent mass of fiber loaded divided by the volume of dye waters associated with the initial dye
operation. In the case of a direct dye for a fiber mass of 1000 lb, the mass of salt can be 1000 lb in a
volume of approximately 1000 gal. Significant amounts of paraffin wax are contained in the wastewater generated from the bleaching process.
The dyeing or painting process is conducted using either Beck or jet dyeing machines. The greatest
portion of the waste materials is made up of spend dyes and chemical auxiliaries. In addition to dyes,
five basic types of chemicals are used, a sequestrant, a surfactant, a leveling agent, a carrier and a pH
adjuster. The carrier is typically biphenyl which allows the dyes to penetrate the polyester fibers; an
after scour is used to wash out carriers and excess dyes. Waste waters are typically around 180°F.
Bleaching is carrie dout in a J-Box machine. Beck dyeing is a batch process whereby, the fabric is dyed
in heated atmospheric dye becks containing dye batch mixtures with constant movement of the cloth
through the batch until the desired shade is obtained. The dye batch is then discarded, the fabric is
rinsed in the Beck and is then sent to the dryer. Jet dyeing is also a batch process, only the fabric is
stationary and the dying process occurs in heated pressurized reactors. Around 15% of the dyes
originally introduced into the cotton fiber batches are discharged; around 50% of the dyes introduced
into the synthetic fiber batches are discharged. Most of the auxiliary chemicals added to the batches
are present in the discharge. These wastewaters contain priority pollutants in the form of aromatics,
halogenated hydrocarbons and heavy metals. Dyehouse wastewaters therefore, contain a wide variety
of direct colorants, reactive colorants, dispersed colorants, organic solvents, inorganic and organic
47th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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