The expected reduction of VSS concentration was observed only
with the addition of 50 mg/L biosurfactant directly into the reactor.
In this operating condition, the VSS concentration in the Control
bioreactor was 2828 318 mg/L, while in the Test bioreactor,
1800 451 mg/L. Considering the entire operation period under
this condition (from days 149 to 181), TSS disposal was 36% lower
in the Test bioreactor (53 13 mg TSS/day) compared to value
observed in the Control bioreactor (83 8 mg TSS/day). This
difference, even considering the standard deviations observed,
would be significant in the Student t test. However, Fig. 1B shows
that the reduction of solids did not occur early in the period, but
after six batches with the addition of higher biosurfactant
concentration. Previous experiments conducted with other bioproducts
have shown the need for an extended exposure time so
that the reducing effect could be observed [7]. After this initial
period, a more pronounced effect of biosurfactant was observed,
with average VSS concentration in the Control bioreactor of
3061 189 mg/L and the Test bioreactor of 1435 196 mg/L. Thus,
considering only the period from days 163 to 181, TSS disposal was