The effect of influent pH on the COD removal is presented as
response surface plots in Fig. 1. It was observed that at constant distance
between electrodes and external resistance,the COD removal
decreased with increase in pH. For example, COD removal rate,
expressed with respect to cathode surface area, in SMFCs operated
with a feed pH of 6.5 and 8.5 was 3.81 g m−2 d−1 and 1.77 g m−2 d−1,
respectively when the distance between electrodes was 50 cm and
the external resistance, 0 i.e. short circuited mode of operation.
SMFCs operated with feed pH of 6.5 were reported to give higher
COD removal than feed pH of 8.5 (Sajana et al., 2013a).