Dyeing and Printing

Dyeing And Printing 3(2+1)

Lesson 16 : Pollution Through Dyeing And Printing

Main Pollutants Present In The Effluents

The textile dyeing and printing industries effluent contain high COD and Colour it was observed that, the pollution potential of the printing industries is negligible as compare to that of textile dyeing. Pollution of water resources is thus high, as their location is mostly on the banks of Small River.

Textile mills discharge large quantity of effluent water into public sewerage or surface water on the open land that is to be treated up to certain tolerances limits. An average sized mill having cloth production of about 8000 kg per day discharges about one million liters of effluent water per day.

• Industrial effluent discharged from dyeing industries largely contains alkalis, residual dyes, starches and cellulose, soluble salt with mainly sodium and calcium silicate, oils and other impurities.
• As a result of effluents, ground water quality and potentiality of rivers are rapidly deteriorating.
• The use of this polluted ground water for irrigation has also sharply reduced cropping intensity, crop production and density.
• The use of polluted water for growing food and fodder crops and for drinking purposes has also created health hazards for the human and live stock pollution.

The three major types of wastes in the printing industry include:

1. Solid Wastes - In a general printing environment solid waste could consist of the following: empty containers, used film packages, outdated materials, damaged plates, developed film, dated materials, test production, bad printing or spoilage, damaged products, and scrap paper.
2. Wastewater - Wastewaters from printing operations may contain lubricating oils, waste ink, cleanup solvents, photographic chemicals, acids, alkalis, and plate coatings, as well as metals such as silver, iron, chromium, copper and barium.
3. Air Emissions - Printing operations produce volatile organic compound (VOC) emissions from the use of cleaning solvents and inks, as well as alcohols and other wetting agents (used in lithographic printing). Larger plants can be the source of NOx and SO2 emissions.

Textile wet processing (i.e. preparation, dyeing, printing and chemical finishing) has always been considered one of the worst industrial sectors in terms of water consumption and pollution.