3.2. Influential factors on the removal of ammonium and manganese
3.2.1. Effect of temperature
As shown in Fig. 3A and B, as the temperature decreased from
22.2 C to 6.6 C, the removal efficiency decreased from 92.0 to
87.8% for ammonium and from 99.5 to 89.9% for manganese, indicating
that the filter film still had a high oxidation activity when
the temperature was down to 6.6 C. Temperature plays an important
role in biological processes. Andersson et al. [26] proposed
that only 10–40% of ammonium was removed at 4–10 C in a pilot
scale filter. Although some researchers have found that full nitrification
could occur at lower temperatures, special measures should
be adopted to facilitate this, such as isolation of functional bacteria
(Acinetobacter sp) [27], stepped increase in DO concentration [28]
or dosing with phosphoric acid [29,30]. Berbenni et al. [31]
reported that manganese oxidation by microbes was inhibited at
temperature lower than 14 C. Thus, it was deduced that chemical
catalytic oxidation not biological processes may be responsible for
the removal of ammonium and manganese, because the chemical
catalytic oxidation is more adaptable to the changes in environmental
factors than that of biological oxidation. As shown in
Fig. 3C and D, as the temperature decreased from 22.2 C to
5.6 C, the reaction rate k decreased from 0.32 min1 to 0.13 min1
for ammonium. Reduction in temperature can lead to a decrease in