Section 14. TEXTILE WASTES
CASE HISTORIES: CARPET MANUFACTURING
WASTEWATER TREATMENT IN MUNICIPAL PLANTS
Robert W. Troxler, Program Manager
Kun S. Hopkins, Principal Engineer
Environmental Protection Division
Georgia Department of Natural Resources
Atlanta, Georgia 30334
The carpet industry in the United States is concentrated in northwest Georgia. Approximately 50% of the nation's carpet is produced in an eight-county area. In 1980 about 500
million yards of carpet were produced in the area with a mill value of approximately $2.5
bdlion. Most of the industry's wastewaters are treated at 12 municipal wastewater treatment
plants.
These wastewater treatment plants have been treating carpet finishing wastewaters from
2 to 18 years, depending on the plant. A great amount of information about carpet manufacturing wastewater and treatment of this wastewater in municipal plants has been obtained. The purpose of this paper is to summarize this information and to point out ways of
minimizing water pollution from this industry.
MANUFACTURING PROCESS
Carpet may be made of at least seven different fibers. Nylon is used in over 70% of all
carpet. Nylon, polyester, polypropylene and acrylic account for over 95% of production.
Dyeing and finishing operations are different for each fiber type. Polypropylene and acrylic-
fibers are colored before being tufted into carpet. Nylon and polyester fibers are primarily
piece dyed.
In 1970 most carpet was dyed in becks or was printed. Introduction of continuous dyeing
machines began in 1968. Many continuous machines were installed during the 1970's. It is
now estimated that approximately 50% of all carpet is dyed on continuous machines.
Printing accounts for a small portion of carpet being dyed today.
Almost all polyester is beck dyed. Nylon may be either beck dyed or continuously dyed.
Acid or disperse dyes may be used to color nylon. Disperse dyes are used almost exclusively
to dye polyester.
Beck Dyeing
Beck dyeing is a batch process whereby greige carpets are dyed in heated atmospheric
dye becks containing dye bath mixtures with constant movement of carpet through the bath
until the desired shade is reached. The dye bath is then discarded, the dyed carpet is rinsed
in the beck, and is then sent to the dryer. Figure 1 illustrates an atmospheric dye beck.
Dye bath chemicals in beck dyeing of nylon usually consist of dyes, leveling agents, se-
questrants, surfactants, and pH control agents. Beck dyeing of polyester is similar except
that dye carriers must also be added to some polyester formulations.
The average cycle time for a beck is four to five hours. Water use is approximately 10 to
20 gallons per pound of carpet.
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