Results show that overall COD removal rates were highest for
granule-based HUASB-aerobic and AHR-aerobic treatment combinations
(Table 1), whereas highest methane yields were observed
in the non-granule AnCSTR-aerobic system (Fig. 3). Therefore, neither
the granule nor non-granule systems were clearly superior in
terms of treatment performance; other factors must be considered.
The key question is whether the poor methane yields in the granule
based system were important relative to overall energy balance
in the system; i.e., the granule-base anaerobic units have
low methane yields, but they also produce lower COD effluents,
which require less aeration in the subsequent aerobic step.