A Literature Review of the Efficacy of Natural Systems in
Removing Faecal Indicator Bacteria Two wetland types have been
distinguished according to the presence of a free water surface.
This feature determines the extent to which key processes,
including oxygen diffusion and the balance of removal mechanisms
between sedimentation and sieving, will operate. Removal of
faecal indicator organisms and pathogens has been represented as
a two step process, where initial retention is followed by
elimination. Short-term by-pass and channelled flow, which might
occur during storm-events, represents a potential problem to
operational efficiency. Despite this fact, almost no intensive,
event-based, sampled data exist. The majority of studies rely
upon infrequent (weekly or longer) paired sampling of influent
and effluent flows which are likely to be biased towards more
stable flow conditions. Few data quantify seasonal changes to
FIO and pathogen populations within individual wetlands. Thus,
the principal data gap is ev