Pollution Prevention Guidelines to provide technical advice and guidance to staff and consultants involved in pollution-related projects. The guidelines represent state-of-the-art thinking on how to reduce pollution emissions from the production process. In many cases, the guidelines provide numerical targets for reducing pollution, as well as maximum emissions levels that are normally achievable through a combination of cleaner production and end-of-pipe treatment. The guidelines are designed to protect human health; reduce mass loadings to the environment; draw on commercially proven technologies; be cost-effective; follow current regulatory trends; and promote good industrial practices, which offer greater productivity and increased energy efficiency.
Table of Contents
- Industry Description and Practices
- Waste Characteristics
- Pollution Prevention and Control
- Target Pollution Loads
- Treatment Technologies
- Emissions Guidelines
- Monitoring and Reporting
- Key Issues
Industry Description and Practices
The textile industry uses vegetable fibers such as cotton; animal fibers such as wool and silk; and a wide range of synthetic materials such as nylon, polyester, and acrylics. The production of natural fibers is approximately equal in amount to the production of synthetic fibers. Polyester accounts for about 50% of synthetics. (Chemical production of the polymers used to make synthetic fiber is not covered in this document.)
The stages of textile production are fiber production, fiber processing and spinning, yarn preparation, fabric production, bleaching, dyeing and printing, and finishing. Each stage generates wastes that require proper management. This document focuses on the wet processes (including wool washing, bleaching, dyeing, printing, and finishing) used in textile processing.
Textile production involves a number of wet processes
that may use solvents. Emissions of volatile
organic compounds (VOCs) mainly arise
from textile finishing, drying processes, and solvent
use. VOC concentrations vary from 10 milligrams
of carbon per cubic meter (mg/m3) for
the thermosol process to 350 mg carbon/m3 for
the drying and condensation process. Process
wastewater is a major source of pollutants (see
Table 1). It is typically alkaline and has high
BOD—from 700 to 2,000 milligrams per liter
(mg/l)—and high chemical oxygen demand
(COD), at approximately 2 to 5 times the BOD
level. Wastewater also contains solids, oil, and possibly toxic organics, including phenols from dyeing and finishing and halogenated organics from processes such as bleaching. Dye wastewaters are frequently highly colored and may contain heavy metals such as copper and chromium.
Wool processing may release bacteria and other pathogens. Pesticides are sometimes used for the preservation of natural fibers, and these are transferred to wastewaters during washing and scouring operations. Pesticides are used for mothproofing, brominated flame retardants are used for synthetic fabrics, and isocyanates are used for lamination The use of pesticides and other chemicals that are banned in OECD countries is discouraged and in general, is not acceptable.
Wastewaters should be checked for pesticides such as DDT and PCP and for metals such as mercury, arsenic, and copper. Air emissions include dust, oil mists, acid vapors, odors, and boiler exhausts. Cleaning and production changes result in sludges from tanks and spent process chemicals, which may contain toxic organics and metals.