It is true that besides the "scientific" design, it is quite easy that the system would fail due to improper civil construction.. I suppose the system you tested was with surface flow, which usually is not that deep (30-40 cm of soil and a water column of 10-30 cm on top of it). The applications for water contaminated with oil hydrocarbons are the most challenging in any case. Especially the one you tested, which contained bitumen.
Published by Alexandros Stefanakis, Constructed Wetlands Specialist
It is true that besides the "scientific" design, it is quite easy that the system would fail due to improper civil construction.. I suppose the system you tested was with surface flow, which usually is not that deep (30-40 cm of soil and a water column of 10-30 cm on top of it). The applications for water contaminated with oil hydrocarbons are the most challenging in any case. Especially the one you tested, which contained bitumen.