ABSTRACT
Textile industries generate huge quantities of wastewater from various steps in the dyeing and finishing processes (Desphande, 2001). Nearly 2% of the total worldwide production of dyes is discharged directly as aqueous effluent. Further, almost 10% are lost during the textile dyeing process. The efficiency of application of color in the form of dyes onto textile fibers is not a very efficient process (Nigam et al., 1996). The efficiency of color application varies depending on the method of dye delivery. Consequently, the wastewater produced by the textile industry is generally colored as a result of unfixed dyes (Shu et al., 2005). Certain classes of dyes like reactive dyes are generally found at relatively high concentrations in wastewater. This is a result of their lower ability of fixation to fibers like cotton and viscose. These wastewater streams are often found to be biorecalcitrant due to the presence of various additional chemicals like fixation agents, bleaching agents and surfactants. Large amounts of salts are added to the dye baths for improving dye fixation. Salt concentrations at high levels of up to 100 g/L are necessary for reactive dyes (Mauersberger et al., 1948). In addition to salts, caustic solution of about 23% NaOH is also added to improve properties like fiber strength, shrinkage resistance, luster, and dye affinity. The escalating problem of synthetic dyes is
8.1 Introduction .......................................................................................................................... 133 8.2 Conventional Methods for Treatment of Wastewater ........................................................... 134 8.3Membrane Separation Processes .......................................................................................... 135 8.4Objective of the Study .......................................................................................................... 136 8.5Experimental ........................................................................................................................ 136
8.5.1 Membrane ................................................................................................................. 137 8.6Results and Discussion ......................................................................................................... 138
8.6.1Scheme 1: AOP Followed by NF .............................................................................. 138 8.6.2Scheme 2: Two-Step NF ........................................................................................... 140 8.6.3Hydrodynamic Studies ............................................................................................. 144 8.6.4 Turbulent Promoters ................................................................................................. 144
8.7Conclusions ........................................................................................................................... 144 References...................................................................................................................................... 145
that due to their recalcitrant nature, they are a major contributor to pollution in the aquatic environment, which has led to the enactment of strict environmental regulations (Hessel et al., 2007).
