Haridas et al. [42] operated a Buoy

Haridas et al. [42] operated a Buoyant filter bioreactor (BFBR)
packed with polystyrene balls and biogas was reintroduced to
the reactor to fluidize the bed material and prevent the clogging.
COD removal efficiency was above 85% during the treatment
of simulated milk wastewater at OLRs applied. Increase in OLR
enhanced biogas production, and methane yield was 0.37 m3 kg−1
CODremoved at OLR of 10 kg COD m−3 d−1 which was 100% close to
theoretical value. Scum formation inside the BFBR was observed
during the increment of OLR; however, accumulated scum was
degraded when wastewater feeding stopped. Comparing the COD
performance and CH4 yield in Table 3 indicates that BFBR is the
superior on other bioreactors. Although Buoyant provided the
highest methane yield among in biofilm reactors, scum accumulation
could be a barrier that may limit the widespread application
with real dairy wastewater. Further studies should be directed to
develop strategies to overcome the scum formation with real dairy
wastewater at various operational conditions.