Nanomembranes - Nanotechnologies for Water Environment Applications - page 393

water conservation policy and an increasing concern of water scarcity, water reclamation
and reuse would need to be practiced in high water consuming industries.
Table 12.11 Potential applications of NF for industrial effluent treatment.
Industry Applications

Textile Water reclamation and reuse

Color removal and recovery
Recovery of salts

Landfill Leachate Removal of organics and multivalent ions

Metal Processing Recovery of heavy metals

Recovery of eluant

Electroplating Industry Water reclamation and reuse

Removal and recovery of anions and cations

Food Processing Industry Removal of organics in the wastewater

Protein, enzyme and aroma recovery

Pulp and Paper Processing Industry Water reclamation and reuse

A typical textile processing factory follows a 4-stage production process which
made up of formation of yarn and fabric, wet processing and fabrication. Majority of the
textile wastewater is generated from the wet processing operations. An amount of 50-
100% of the color used is fixed on the fiber during dyeing and printing processes, while
the remainder is discarded into the wastewater (US EPA, 1997). Table 12.12
summarizes the different classes of dyes and the associated pollutants.

Dye is one of the most recalcitrant pollutants to be treated in the textile
wastewater. Previously, color dying effluents are only treated to meet the discharge
standards due to the limitations of the conventional treatment facilities which include
biological and physical-chemical processes to meet the process water quality. The
conventional biological systems such as activated sludge had been reported to be
ineffective in decolorizing the textile effluents. This leads to a high color content of the
discharged water (Tang and Chen, 2005). Advanced treatment using various oxidizing
agents such as ozonation and hydrogen peroxide/ultraviolet (UV) were also reported to
be inefficient in decolorizing the effluent due to the high resistant of complex aromatic
molecular structure of dyes (Marmargne and Coste, 1996; Ciardelli et al., 2001).

Generally, the effluent from this industry contains a large amount of dyes, salts
(typically 40-80 g/L) and chemical oxygen demand (COD) (from additives such as