Then {HEAD ~ the surfaces} are sprayed with {TAIL ~ water} and the effluent is discarded, or recovered, if desired 
are sprayed with
Then { HEAD ~ the surfaces } are sprayed with { TAIL ~ water } and the effluent is discarded , or recovered , if desired
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH