Constructed wetlands for wastewater treatment in central Italy.

The performance of 4 constructed wetlands designed by IRIDRA Srl and operating in Tuscany (central Italy) has been monitored during the last three years. The 4 treatment systems have different sizes and characteristics: one single stage secondary treatment (150 p.e.); two secondary treatment plants with effluent reuse: one small (60 p.e) and the other big (350 p.e.); a tertiary treatment of effluents from an activated sludge plant with high hydraulic load fluctuation (5-500 p.e.). Due to geographical and economic constraints the four systems have high hydraulic and organic loading rates, neverthless the systems show very good removal performance of COD (62-95%), especially the ones with higher inflow COD concentrations (87-95%). Interesting results concerning also removal percentage of MBAS (42-88%) and ammonium (42-85%) were obtained, even though NH4+ concentration in the outflows of some of the plants, doesn't always comply with Italian quality standards.