Page 71 - Materials Chemistry, Second Edition

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Sustainable Industrial Design and Waste Management
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out of the dye from the fabric. However, both sodium sulfide and acidified
dichromate are toxic and hazardous to handle. Their usage may leave harmful
residues in the finished fabric and generate effluents that are difficult to treat
and that damage the environment.
This project was implemented by the Egyptian Environmental Affairs
Agency “EEAA” through the SEAM Program in three different factories –
El-Nasr Spinning and Weaving, Dakahleya Spinning and Weaving and AmirTex –
at no capital cost and resulted in cost savings of 2–16% on consumable
materials (SEAM, 1999d). The measures implemented by the SEAM project
demonstrate how sodium sulfide and dichromate can be safely substituted
without a decline in fabric quality. As a result the advantage of sulfur black
can be retained, whilst eliminating the adverse environmental and health
impacts. Other benefits included the elimination of toxic and hazardous
materials from the workplace and environment, reduced wastewater treat-
ment costs, improved fabric quality, and increased productivity.
El-Nasr Spinning and Weaving is a large public sector factory built in
1963 and currently employing 7,000 staff. It processes an average of 8,000 tons
of raw fabric per year, of which 20% is spun cotton yarns, 12% is polyester
blend yarns, and 68% is gray fabric. The main products are cotton or blended
yarns, white and dyed cotton and blended fabrics. Approximately 52.5 million
meters of fabric were produced annually.
Dakahleya Spinning and Weaving is a public sector company with annual
production of 11,400 tons of spun yarns and ready-made garments. The factory
was built in 1965 and employs 4,000 staff. It comprises three spinning depart-
ments, an open end spinning unit and a tricot plant with a weaving unit, a dye-
house and a tailoring hall. The main products are cotton yarns, cotton knitted
fabrics, polyester blended fabrics, and ready-made knitted cotton garments.
AmirTex is a privately owned company with around 100 employees. The
factory was built in 1984 and comprises a weaving and knitting department, a
printing unit and a dyehouse. The main products are cotton yarns, cotton knit-
ted fabrics, polyester blended fabrics, and ready-made knitted cotton garments.
Average annual production is 720 tons of cotton, polyester and blended fabrics.

Opportunity assessment
The following CP opportunities were identified in the sulfur black dyeing
process through an industrial audit:

• High sulfur content in the dyehouse wastewater of 40–170 mg/l.
• Acidified dichromate resulted in concentrations of hexavalent
chromium of 27 mg/l in the dyehouse wastewater.
• Bad odor resulting from the use of sodium sulfide in the dyeing process.
• Worker safety issues associated with the handling of toxic and haz-
ardous chemicals.
• High steam, energy and water consumption was noted during the
sulfur black dyeing process.
• Fabric losses resulting from the presence of excess sulfur on the material.