That is, as effluent is admitted to the vessel the rate at which liquid is withdrawn from the vessel is determined by {TAIL ~ the rate} at which a liquid constituent of the effluent enters the vessel so as to maintain the preselected level of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That is , as effluent is admitted to the vessel the rate at which liquid is withdrawn from the vessel is determined by { TAIL ~ the rate } at which a liquid constituent of the effluent enters the vessel so as to maintain the preselected level of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