The multiservice company PubliSer SpA has constructed and monitored the ope
ration of a multistage tertiary constructed wetlands wastewater treatment p
ilot plant for experimental and demonstration purposes. The facility was de
signed by and is partially monitored by the environmental engineering compa
ny WS SaS in Cerbaia, Florence, Italy. The experimentation with natural was
tewater tertiary treatments is particularly important within central Italy
as there are recurring environmental problems related to the poor functioni
ng of small wastewater treatment systems. The present study is designed to
compare the utility and efficiency of different multistage configurations f
ollowing an active sludge process through an intensive monitoring programme
that was initiated in November 1997. In this paper, we report the principa
l design specifications, a detailed description of the pilot plant, the dim
ensioning criteria and an analysis of the influent and effluent characteris
tics (COD, BOD, N, P, microorganisms, TSS, etc.) for each compartment monit
ored in the first period of plant operations. The pilot plant consists of t
wo experimental lines, each characterised by a first and second treatment s
tage. The effluents of the first stages are divided into three different se
cond-stage basins. The plant demonstrated high removal of nutrients, a good
buffering capacity and a reasonable reduction of microorganisms after only
a limited number of months of operation. Continued monitoring and comparis
on of the different constructed wetland strategies is providing interesting
information for future designs and operation. (C) 1999 IAWQ Published by E
lsevier Science Ltd. All rights reserved.