The water and gas delivery rates are controlled to satisfy the following relations: ##EQU1## wherein {HEAD ~ Q1} is {TAIL ~ the delivery} of oxygenated gas in m3 /hr, 
is
The water and gas delivery rates are controlled to satisfy the following relations : # # EQU1 # # wherein { HEAD ~ Q1 } is { TAIL ~ the delivery } of oxygenated gas in m3 /hr ,
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH