{HEAD ~ Tailings} are recycled back into the reactor and combined with {TAIL ~ fresh feed} for bubble control 
are combined with
{ HEAD ~ Tailings } are recycled back into the reactor and combined with { TAIL ~ fresh feed } for bubble control
HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH