Previous studies showed that iron (Fe2+) increases the granulation of anaerobic granular sludge in UASB reactors [17]. The effects
of zero-valent iron (ZVI) on anaerobic granular sludge were also
investigated. The observations are explained by (i) the ZVI reaction benefiting the growth of methanogens through acid buffering
and the reduction of the oxidation–reduction potential and (ii)
Fe2+ leaching from ZVI advancing the granule aggregation [18].
However, there is no information on the effects of ZVI on aerobic
granulation.