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waste in many wet processing operations amounts to as much as 2% of the fabric processed.

Unlike water and solid waste, no comprehensive study has been published on air pollution from textile operations. Textile mills produce atmospheric emissions from all manner of processes, and these have been identified as the second greatest problem for the textile industry [8]. There has been much speculation about air pollutants from textiles but, in general, air emissions data for textile manufacturing operations are not readily available [9-11]. Most published data are mass balance not direct measurements [12, 13]. Direct reading tubes and gas chromatog-raphy/mass spectrometry (GC/MS) have been used more recently to get more reliable data [14, 15]. Hopefully, in the future air emissions data will continue to be collected from textile operations, and better definitions of industry norms can be expected. Considerable effort is now underway in that regard [14, 16].

Primarily because of nitrogen and sulfur oxide emissions from boilers, most textile plants are classified as major sources of hazardous and toxic air emissions under EPA regulations. Once classified as a major source, all air emissions (even trace emissions) from unit processes in the facility fall under a high level of regulation. Unit operations of concern for air emissions are printing, coating, finishing, and dyeing. Within these general facility identifications, specific point sources and general area sources generally include boiler stacks, coating operations, ovens, solvent processing units (e.g., dry cleaning), dyeing machines, mix kitchens, drug rooms, and storage tanks.

Fabric coating operations are worth special note in regard to air emissions. Although the number of coating operations is very small, they typically emit a higher level of offensive air pollutants than other types of textile manufacturing. The solvent content of the air in coating ovens can reach levels of several percent by weight. Published data concerning coating solvent losses are not readily available, but it is not unusual to find tens and even hundreds of thousands of pounds of methyl ethyl ketone (MEK), methyl isobutyl ketone (MIK), toluene, xylene, and dimethyl formamide emitted from coating processes in a large facility. These losses come from bulk tank, mix kettles, holding drums, churn mills, mixers, knife coaters, oversprays, and drying and curing equipment. In most cases, capture efficiency is a limiting factor in effectively treating these emissions. Recovery systems are readily available from various suppliers and, as the cost of solvents and supplemental incineration fuels rise, recovery will become more and more attractive economically. A long-term solution is to develop water-based, nonvolatile or less hazardous solvent types.

In addition to coating operations, lower levels of emissions come from widely used processes such as heat setting, thermofixation, and drying and curing ovens in conventional fabric finishing. Typical operating temperatures are 300°F for drying, 360°F for curing of finishes, 400°F for thermofixation of dyes, and 375°F for heat setting. Many materials not normally regarded as volatile will vaporize under these conditions.

Another significant source of air emissions is breathing losses from vented bulk storage tanks. When liquid is drawn out of these tanks, when air cools, or when the ambient atmospheric pressure rises, air enters the tank. When the tank is filled, temperature rises, or the barometric pressure falls, air is expelled. When the material stored in the tank contains volatile components, the expelled air constitutes an emission source.

In addition to point sources, significant air emissions can arise from sources such as solvent-based cleaning activities (cleaning and maintenance), spills, wastewater treatment systems, general production area ventilation, and warehouses (especially formaldehyde-emitting fabric storage). Fugitive emissions and spills can be important, especially for a highly dispersible waste form such as airborne pollution [17].

Aeration of secondary activated sludge biological treatment lagoons strips volatile components of the mixed liquor, and these emit from the waste treatment system as a general area source. Volatile components of spent processing baths (e.g., dye carriers, solvent scouring agents, and machine cleaners) as well as degradation products of these components can reasonably be expected to strip and emit during the treatment process. No data on this have been made public at this time.

Fabric stored in warehouses can produce volatile emissions from process residues, especially printing, dyeing, or finishing chemicals that remain in the fabric. The most important of these is formaldehyde, but others, notably hydrocarbons (e.g., from softeners and wax water repellent finishes), can be present.

Spills can emit volatile air pollutants for months and even years. These are not unusual in off-loading areas and within the berms of bulk storage areas.

Common air pollutant emissions from ovens include mineral oil, knitting oils, fiber finishes, softeners, hydrocarbons, urea from printing or continuous thermofix fiber reactive dyeing, and volatile dyebath additives that are sorbed by substrate and then released during subsequent heat setting, drying, and curing [15, 18, 19].

Fugitive/area emissions include not only formaldehyde and hydrocarbons from warehouses but also processing chemicals from routine handling, wastewater treatment systems, and spills.

7.1.5. Indoor Air Pollution

Indoor air quality can be adversely affected by materials that emit pollutants (primary emitters), as well as by materials that sorb and reemit pollutants [16]. In the United States, the Occupational Safety and Health Administration (USHA) proposed an indoor air quality rule that will affect 21 million workers and that will require the development and implementation of indoor air compliance programs [20]. At this time, primary emissions from several process residues (chemical finishing, dyeing, printing, assembly, and product fabrication) are under study [16, 20]. In addition, sorption/reemission characteristics of textile materials are of interest. Tests of air emissions from various products including draperies have been done. In one study, drapes were found to emit indoor air pollutants

Table 7.3 Emissions Detected from Drapes [21]

From Drapery Material

Table 7.3 Emissions Detected from Drapes [21]

From Drapery Material

Acetone

Decane

2,5-Dimethylfuran

Toluene

Benzaldehyde

Decenal

1,4-Dioxane

1,1,1-Trichloroethane

Benzene

Dichlorobenzene

Ethanol

Trimethylbenzenes

Butanol

1,2-Dichloroethane

Methylene chloride

m -Xylene

p -Xylene

Chloroform

Dimethyldisulfide

Tetrachloroethene

plus 100 more VOCs

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