3. Results and discussion
Experiments on decolorization using simulated wastewater
under laboratory condition were performed. Initial experimental
conditions with flasks containing BSM and 56 mg/l
of dye mixture incubated under shaking condition, were not
able to decolorize dye even after 72 h. Shaking conditions removed
COD by 59.20%, but decolorization only 20%. When
the same medium was incubated under static conditions at
30 ◦C, decolorization was observed within 16–20 h, indicating
that aeration arrested azoreductase enzyme secretion
thereby inhibiting decolorization. Hu [19] has also observed
that facultative bacteria are able to decolorize dyes under microaerophilic
condition. Typical results of growth consortia
and decolorization in the presence of simulated wastewater
are given in Figs. 1 and 2, respectively. This along with COD,
BOD reduction (Table 3) clearly shows that decolorization
occurs during the logarithmic growth phase (within 24 h)
and COD/BOD reduction during the maximum stationary
growth phase. A similar observation was reported by Knapp
and Newby [25] for effluent containing nitrated stiben sulphonic
acid. The pH of the medium always shifted to the
alkaline range (7.0–7.3) and this may be due to the formation
of ammonia from aromatic amines. When the medium
was incubated under static conditions COD reduction was
only 81.40% even after 5 days of incubation and microbial