The reactors also demonstrated relatively various nutrient
removal performances. More than 50% of acetate was utilized during
the anoxic feeding phase in SBR40, while in SBR30 and SBR50 less
than 50% of acetate was consumed during 60 min of anoxic feeding
phase. However, the leftover acetate was utilized efficiently during
the aerobic phase apparently due to the presence of most of the
substrate (oxygen and nitrate) which is advantageous for the
uptake rate of acetate by the microorganisms as described by de
Kreuk et al. (2005b) leading to the highest removal rate of
98.17% for COD at 50 C, while 95.37% and 85.37% removal rate
of COD achieved at the temperature of 40 C and 30 C, respectively
which is comparable to previous situation reported by Song et al.
(2009) in synthetic wastewater treatments using aerobic granules.
Nitrification process also took part quite differently for all the reactors
with the production of nitrite and nitrate. Interestingly, excellent
ammonia removal started to happen in SBR30 after 2 weeks of
operation, meanwhile for SBR40 and SBR50, great ammonia removal
began after 3 weeks of operation. This occurred perhaps due to
assimilation of biomass formation (Song et al., 2009). The highest
ammonia removal rate was 97.50% achieved at 30 C, whereas
ammonia removal rate at 40 C and 50 C were 94.64% and
94.45%, respectively which is comparable to the results in previous
publications by Song et al. (2009) in treating synthetic wastewater
using aerobic granular sludge.