Categorization of Waste Generated in Textile Industry:
Textile waste is broadly classified into four categories, each of having characteristics that demand different pollution prevention and treatment approaches. Such categories are discussed in the following sections:
1.Hard to Treat Wastes
This category of waste includes those that are persistent, resist treatment, or interfere with the operation of waste treatment facilities. Non-biodegradable organic or inorganic materials are the chief sources of wastes, which contain colour, metals, phenols, certain surfactants, toxic organic compounds, pesticides and phosphates. The chief sources are:
Colour & metal dyeing operation
Phosphates preparatory processes and dyeing
Non-biodegradable organic materials surfactants
Since these types of textile wastes are difficult to treat, the identification and elimination of their sources are the best possible ways to tackle the problem. Some of the methods of prevention are chemical or process substitution, process control and optimization, recycle/reuse and better work practices.
2. Hazardous or Toxic Wastes
These wastes are a subgroup of hard to treat wastes. But, owing to their substantial impact on the environment, they are treated as a separate class. In textiles, hazardous or toxic wastes include metals, chlorinated solvents, non-biodegradable or volatile organic materials. Some of these materials often are used for non-process applications such as machine cleaning.
3. High Volume Wastes
Large volume of wastes is sometimes a problem for the textile processing units. Most common large volume wastes include:
High volume of waste water
Wash water from preparation and continuous dyeing processes and alkaline wastes from preparatory processes
Batch dye waste containing large amounts of salt, acid or alkali
These wastes sometimes can be reduced by recycle or reuse as well as by process and equipment modification.
The following operations in textile industry generate highly dispersible waste:
Waste stream from continuous operation (e.g. preparatory, dyeing, printing and finishing)
Print paste (printing screen, squeeze and drum cleaning)
Lint (preparatory, dyeing and washing operations)
Foam from coating operations
Solvents from machine cleaning
Still bottoms from solvent recovery (dry cleaning operation)
Batch dumps of unused processing (finishing mixes)