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