To assess these options, volatile fatty acid (VFA) and long-chain
organic compounds analysis (e.g., long-chain organics, including
lipids), SEM, and molecular microbiological characterisation was
performed on the different anaerobic units. VFA level in anaerobic
reactors can indicate incomplete hydrolysis and fermentation reactions.
However, significant VFA accumulation was not detected in
any of the anaerobic reactors. In contrast, significant differences
in long-chain organic (e.g., lipids) content were noted among reactor
granules and flocs. Specifically, the long-chain organic content
of HUASB and AHR granules increased over reactor operations by
41% and 7.4%, respectively, whereas no similar change was observed
in AnCSTR floc. Therefore, long-chain organics appear to
have specifically accumulated in the granular reactors, which hint
that the granules became coated with such compounds during
reactor operations.