1. Introduction
Vertical-flow constructed wetlands (or soil filters,
or reed bed systems) have become a common treatment
selection of urban wastewaters during the last
decade. They are attractive in specific cases, where other natural systems cannot be easily applied, due
to the relatively small surface requirement and their
high purification efficiency in terms of organic matter
and ammonia, although their efficiency is smaller
in phosphorus removal; Fisher (1998) reported a 20%
P removal by gravel wetland. Vertical-flow systems
are intermittently flooded and drained, allowing air to
refill the soil pores within the bed. The dimensioning
of the vertical-flow constructed wetlands varies widely
between 1 and 2m2/p.e. and up to 5m2/p.e.