The multiservice company PubliSer SpA has constructed and monitored the operation of a multistage tertiary constructed wetlands wastewater treatment pilot plant for experimental and demonstration purposes. The facility was designed by and is partially monitored by the environmental engineering company IRIS SaS in Cerbaia, Florence, Italy. The experimentation with natural wastewater tertiary treatments is particularly important within central Italy as there are recurring environmental problems related to the poor functioning of small wastewater treatment systems. The present study is designed to compare the utility and efficiency of different multistage configurations following an active sludge process through an intensive monitoring programme that was initiated in November 1997. In this paper, we report the principal design specifications, a detailed description of the pilot plant, the dimensioning criteria and an analysis of the influent and effluent characteristics (COD, BOD, N, P, microorganisms, TSS, etc.) for each compartment monitored in the first period of plant operations. The pilot plant consists of two experimental lines, each characterised by a first and second treatment stage. The effluents of the first stages are divided into three different second-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 comparison of the different constructed wetland strategies is providing interesting information for future designs and operation.

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