In this study, statistical experimental design was employed.
These designs have many advantages and were used in many
successful degradative studies (Saravanan et al., 2008). Compared
to conventional one factor at a time experiments, statistical
based factorial design of experiments gave more meaningful
information on the effects, main and interaction, of the factor
involved in the given study. Furthermore, the added advantage
of reduction in the number of experiments to be performed.
Employing such techniques proves more attractive for systematic
investigations without compromising the accuracy of representation
of the environmental system (Montgomery, 2004).