The liquid solution to be separated is pumped past {HEAD ~ the membrane} at {TAIL ~ a controlled pressure} 
at
The liquid solution to be separated is pumped past { HEAD ~ the membrane } at { TAIL ~ a controlled pressure }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL