3.4.1. Estimation of effects of ope

3.4.1. Estimation of effects of operating parameters
The main effect ofthe operating parameters and effects of allthe
two factor and three factor interactions among them (Montgomery,
2006) were estimated after getting the response value ofthe experimental
runs for each set of operating variables (Table 1). From
the Pareto chart, it was observed that pH had the largest effect on
COD removal (Fig. 4a). Negative effect of influent pH and external
resistance on COD removal was observed, indicating reduction in
COD removal with increase in influent pH and external resistance.
Positive effect of distance between electrodes on COD removalindicates that with increase in distance, COD removal increases.
However in case of TN removal, with increase in pH and distance
between electrodes, TN removal increased and with increase
in resistance, it decreased (Fig. 4b). With increase in pH, power
production slightly increased and with increase in external resistance
and distance between electrodes, considerable decrease in
power production was observed (Fig. 4c). All the two factor and
three factor interactions were observed to be less significant for
COD removal, TN removal and power density (Table 2). Within
the operating range selected, main effects of operating parameters
dominated the response COD removal, TN removal and power
density; and the interaction effects were not significant.