Small Wastewater Treatment Plants in Italy: Situation and Case Studies of Upgrading

The choice between centralization and decentralization of wastewater treatment depends on many factors and requires a case-specific approach. Most of Italian plants are small, but they altogether treat only a little fraction of total pollutant load and must comply with different local regulations. This paper reports some examples of upgrading of small overloaded plants with advanced technologies; three plants were upgraded with moving bed biofilm reactors, two plants with dissolved air flotation and a plant with a new line of membrane bioreactors. In all these plants pollutants removal efficiencies improved with minimal additional space request or with just recovery or conversion of existing tanks