The optimisation of COD, NH3eN and 2,4-DCP removal was
conducted using Design-Expert 6.0.10 to determine the optimum
points for the operational conditions to achieve maximum removal
by applying the approximating models given as Eqs. (2)e(4). The
desired goal for the operational conditions was defined as the
maximum value for the IFC, while for the AR, the goal was determined
to be a target of 3.2m3/min to obtain the highest removal for
all responses, especially for NH3eN removal. An initial study of the
AR effect on NH3eN removal indicated that a higher NH3eN
removal (almost 100%) was observed when the AR was greater
than 3.2m3/min (Muhamad et al., 2012b).