usually used to interpret the changes in the aromatics content [37].
The reductions of the absorbance at 254 nm could be attributed to
the direct or indirect attack of molecular ozone or free radicals produced
by ozone decomposition, respectively, on compounds with
the unsaturated bonds, namely carbon–carbon double bonds or
the aromatic rings [30,31]. In addition, use of ozone for the removal
of color of the effluent streams have been demonstrated in the past
for textile industry effluents [38], and also for effluent from a polyester
and acetate fiber dyeing plant [24].
From Fig. 5, it can be seen that the removal efficiencies of the
Color and UV254 are 25.3% and 13.5%, respectively, for the process
of the BAF alone. However, those of the two parameters are
increased to 91.1% and to 82.3%, respectively, for the combined
process of ozonation and BAF. The results indicated that most of
the chromatic group with N@N, C@C and C@O structural of the
organics can be oxidized by ozonation. It also proved that ozonation
conduced to the removal of the Color and UV254 of the BTCW.
Therefore, the present study has demonstrated that the combined
process of ozonation and BAF is effective in treating the coking
wastewater effluent as it can tackle COD, NH4 + AN and the color
problem simultaneously.