5. Conclusions
The research showed that in CW systems for the re-use of
wastewater in agriculture the efficiency of the system is highly
dependent upon the system's water balance. This, in turn, is
strongly influenced by the ET of the macrophytes used in the
system and determining ET is essential in order to be able to
upscale the system. Variations in the water balance of the system,
throughout the growth stages of the species being used,
significantly affect the amount of treated wastewater available
at the outflow. The various species which can be used in a CW
system vary in their aptitude for using available water due to
specific physiological mechanisms. This can lead to greater or
lesser use of water resources, which are unlimited in HSSF system.
The amount of water at the outflow of CWs varies according to the
project aims but it is dependent, however, upon the greater or
lesser ET rate of the species used in the units. It is clear that in dry
areas, where the reuse of treated wastewater is essential for
agriculture, we need to choose those species with a low ETc rate in
order to obtain both good performance levels for contaminant
removal, a reduction in losses from ET and greater amount of water
at the outflow. This aim can be reached by trying also to improve
the main hydraulic features of the system, such as HLR and HRT. As
there is relatively little information available on this subject,
especially in the Mediterranean area, further research is needed,
also regarding Kc values for the species of most interest, in order to
optimize the system efficiency