23    CHEMICAL REDUCTION AND OXIDATION COMBINED
WITH BIODEGRADATION FOR THE TREATMENT OF
A TEXTILE DYE WASTEWATER
Michael W. McCurdy, Graduate Research Assistant
Greg D. Boardman, Associate Professor
Virginia Polytechnic Institute and State University
Blacksburg, Virginia  24060
Don L. Michelsen, Associate Professor
Becky M. Woodby, Laboratory Specialist
Virginia Tech
Blacksburg, Virginia 24061
INTRODUCTION
Consumer demand for brightly colored textile goods has continued since the development of the
first dye. This demand has caused the textile industry to develop new types of fibers and fabrics, new
types of dyes to color these fibers, colors that are brighter and last longer than previous colors, and
new improved methods of dye application.
These new parameters, especially the new dyes, which impart a color to textile wastewater, are of
particular importance in wastewater treatment. The new dyes must yield a color that is bright, and last
throughout the lifetime of the fabric. The stability of the dye refers to the ability of the dye to
maintain its structure and color and of break down with time and exposure to sunlight, water, soap,
soil, and a variety of other parameters. Therefore, when a new dye is made that is stable under all of
these conditions, it becomes more difficult to treat the dye in wastewater.
Because of recent developments in fabrics, dyes, and methods of dyeing, textile wastewater characteristics are very diverse from one mill to the next. The wastewater characteristics can also be highly
variable within the same mill, on a day-to-day or even hour-to-hour basis. The most pronounced
variations include the type of dye in the wastewater and the color of the wastewater.
The treatment alternatives applicable to the removal of color from textile mill wastewaters are also
variable. A certain treatment scheme may be sufficient for one textile mill or even one type of dye, but
not for other mills or types of dyes. The removal of dyes (color) is therefore a challenge to both the
textile industry and the wastewater treatment facilities that must treat these wastewaters. According to
Alspaugh,1 no one specific treatment process can handle the removal of color from all textile wastewaters; therefore, each wastewater has a "tailored solution requiring a combination of methods."
Samples for this research were collected from a textile mill located in Virginia. This textile mill will
be referred to as the Mill for simplicity. The wastewater from the dyeing processes is combined with
municipal wastewater and discharged to a Publicly Owned Treatment Works (POTW) located near
the Mill. The wastewater flow at the Mill is about 3 million gallons per day (MGD). The POTW
treatment system is comprised of extended aeration and aerobic sludge digestion. The POTW has
been successful at removing such wastewater parameters as biochemical oxygen demand (BOD) and
total suspended solids (TSS), but not at removing color.2
The reactive azo dye wastewater stream used in this research was chosen because treatment plant
officials stated that, "the treatment plant had no trouble treating the textile wastewater until the mills
began using reactive dyes." The reactive dye wastewater stream from the textile mill used in this
research is approximately 70% of the Mill's total wastewater stream. The Navy 106 dye consists of
three reactive azo dyes. This wastewater stream comprises approximately 15% of the total wastewater
stream, which correlates with approximately 22% of the reactive dye wastewater stream.3
Recently, state and federal agencies have been requiring lower effluent color limits. This requirement calls for the effluent color to be less than 250 ADMI by 1991 and less than 200 ADMI by 1992.4
46th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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