Abstract
In this work, a four factor three-level Box–Behnken factorial design based on response surface methodology (RSM) was
employed to optimize the removal of phosphate from synthetic wastewater (mineral salts medium-MSM) by the bacterial
consortium (Bacillus sp. RS-1, Pseudomonas sp. YLW-7, Enterobacter sp. KLW-2). A mathematical model was then developed
to show the effect of each medium composition and their interactions on phosphate removal. The effect of the lactose
concentration (X1), pH (X2), time (X3), and agitation (X4) and their interactions on the removal of phosphate by the bacterial
consortium was investigated for an initial phosphate concentration of 100 mg l-1 as a fixed input parameter for the batch studies.
Quadratic models obtained for the response variable predicted optimum phosphate removal (Y1) of 92.2 % in MSM with lactose
corresponding to a bacterial consortium growth of 1.1 in terms of optical density (OD) (Y2) and 0.34 g l-1 as dry biomass (Y3),
after 72 h. The ANOVA results showed that the coefficient determination value (R2) for Y1, Y2 and Y3 were found to be 0.9 and
the experimental values are in good agreement with the predicted ones. The response indicated significant fit of the model to the
experimental data, which confirms that RSM could be effectively used to predict the phosphate removal from wastewater by the
bacterial consortium used in this work.