The linear effect of COD (P < 0.05), pH (P < 0.01) and FPE (P < 0.05) was statistically significant for increasing PNSBsi population, whilst, the linear effect of COD (P < 0.01), pH (P < 0.01) and FPE (P < 0.05) was also statistically significant for reducing ORP value. Both regression equations show significant effects of interacting relationships between the COD vs. initial pH on the PNSBsi population (P < 0.01) and the ORP values (P < 0.01). However, a significant effect of interacting relationships between the initial pH versus the FPE concentration was observed only on the PNSB population (P < 0.05) while a significant effect of the interacting relationship between the COD versus the FPE concentrations was found only on the ORP (P < 0.01).