That is, as effluent is admitted to the vessel the rate at which liquid is withdrawn from the vessel is determined by the rate at which {HEAD ~ a liquid constituent} of the effluent enters {TAIL ~ the vessel} so as to maintain the preselected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That is , as effluent is admitted to the vessel the rate at which liquid is withdrawn from the vessel is determined by the rate at which { HEAD ~ a liquid constituent } of the effluent enters { TAIL ~ the vessel } so as to maintain the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