The research presented in this article describes an investigation into the use of vegetated submerged reedbeds (VSR) as a practicable alternative for effluent treatment for small-scale wine producers. In this study, we found that the hydraulic processes occurring within the VSR display significantly nonideal behavior. If the feed to the VSR was located on the surface the dead volume accounted for approximately 25% of the nonideal behavior of the system and bypass accounted for a further 6%. A preferential flow pattern was found within the VSR with the greatest flow occurring closest the surface and in the center, and the least at the sidewalls. We propose that the flow profile can be conceptualized as being hull shaped and found that this profile was the same for irregularly shaped gravel and for spherically shaped gelatinous beads. We, therefore, hypothesize that it is not dependent on the geometry of the VSR or the packing medium. (c) 2013 American Institute of Chemical Engineers AIChE J 60: 420-431, 2014