That is, as {HEAD ~ effluent} is admitted to the vessel the rate at which liquid is withdrawn from the vessel is determined by the rate at which a liquid constituent of the effluent enters the vessel so as to maintain the preselected level of liquid, or {TAIL ~ liquid bed} 
That is , as { HEAD ~ effluent } is admitted to the vessel the rate at which liquid is withdrawn from the vessel is determined by the rate at which a liquid constituent of the effluent enters the vessel so as to maintain the preselected level of liquid , or { TAIL ~ liquid bed }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH 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