In Step 23, the pumping of the solution and {HEAD ~ the discharging} of the liquid are controlled to {TAIL ~ optimum rates} 
In Step 23 , the pumping of the solution and { HEAD ~ the discharging } of the liquid are controlled to { TAIL ~ optimum rates }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL