concentration and biosurfactant addition method. The use of
different biosurfactant batches, as well as the addition method (in
the feed or directly into the reactor) did not result in significant
differences in the operation of the Test bioreactor. However, the
rhamnolipid concentration influenced the results.
The final pH of batches (after 5.5 h of reaction time) was slightly
higher in the Test bioreactor in some periods of operation, but
remained at values close to 7.0–7.5 in both bioreactors, a value
considered suitable for aerobic biological treatment. Fig. 1A shows
the results obtained in terms of COD removal throughout the
operation period of Control and Test bioreactors. After the
adaptation period (15 days), COD removal efficiencies remained
above 85%, and no significant differences were observed in any of
the conditions evaluated. Values ranging from 80.6% to 97.3% and
84.7% to 97.3% were obtained for Control and Test bioreactors,
respectively. Therefore, the addition of rhamnolipid did not affect
the organic matter removal efficiency in any concentration
evaluated, which is a primary condition for the indication of this
bioproduct as a reducing agent of sludge production in treatment
systems.