Physical–biological hybrid system can achieve significant
energy saving with design such as the upflow anaerobic sludge
blanket (UASB) reactors with submerged aerated biofilters hybrid
system as shown in Fig. 2b [31]. UASB has the ability to stabilize
anaerobically 70% of the organic substrate that is flowing to the
plant. Consequently, there will be low sludge production and a
significant energy saving will be achieved with such hybrid system.
Biofilter serves as the post-treatment for UASB effluent and
able to further degrade the soluble compounds thus filtered the
balanced suspended solid.