Results and discussion
3.1. Effect of recycling on characteristics of effluents
The characteristics of effluents and ozone treated
effluents are given in Table 1. It reveals that the
treatment results in a very slight reduction in TDS
values. This indicates that the ozonation does not have
an effect on the removal of dissolved solids from acid
dye effluents. Further, it can be observed that the ozone
treatment of dye effluent and those obtained from
recycling operations results in reduction of chemical
oxygen demand (COD). But the reduction in COD does
not show any specific trend with respect to increase in
number of recycling operations. Lopez et al. [8] have
observed a reduction in COD in their study on ozone
treatment of industrial textile effluents and stated that it
was due to the reduction of total organic carbon (TOC)
and partial oxidation of organic substrates. Koyunchu
and Afsar and Perkins et al. have also observed a similar
trend in the treatment of reactive dye and acid dye
effluents, respectively [21,22].