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