PILOT PLANT EXPERIENCES ON Escherichia Coli AND NUTRIENTS REMOVAL IN THE UPPER AEROBIC LAYER OF FINISHING LAGOONS FOR WASTEWATER IRRIGATION REUSE

The implementation of good practices in Wastewater Treatment Plants management allows to reach different goals as wastewater reuse, energy production and raw material reservoir. In the last decades the use of natural treatment systems for wastewater reuse is increasing as they are efficient with low energy consumption. Lagoons, also called ponds, are natural or artificial basins commonly used for natural wastewater treatment, where occurring chemical, biochemical and physical natural processes. More in details, three processes are in equilibrium: photosynthesis, aerobic oxidation and anaerobic decomposition. The regulator of this equilibrium is the oxygen availability. In this context this study focuses on the processes occurring in the aerobic layer (around 60cm) of a hybrid natural treatment plant: aerobic lagoon/Phytotreatment FWS with Lemna. This layer is crucial to reduce the concentrations under the legal thresholds of the following nutrients: Nitrogen Ammonia, Orthophosphate, Total Nitrogen, Total Phosphorus and Escherichia coli. The aim of the study is to verify the nitrification and disinfection capacity in this layer. The results are also connected with the management policies adopted. Moreover, the phosphorus variations have been verified in relationship with nitrification. To this aim a pilot plant was built in the Santerno WWTP area in the city of Imola in Italy. The influent flow comes from the outlet of the full-scale plant. Monthly monitoring campaigns have been carried on two sampling points located in input and output of the pilot plant, for one year.