Michela Salvato

Tech-IA floating system introduced in urban wastewater treatment plants in the Veneto region - Italy.

The performance of three integrated wetland treatment plants (horizontal sub-surface flow (h-SSF) and floating treatment wetland (FTW) with differentiated primary treatments) designed for treating domestic wastewater was investigated, monitoring total (TN), nitrate (NO3-N), nitrite (NO2-N) and ammonia nitrogen (NH4-N), total (TP) and phosphate phosphorus (PO4-P), chemical (COD) and biological oxygen demand (BOD5), and dissolved oxygen (DO) at the inlet and outlet of each wetland section from February 2011 to June 2012. Sediments settled in the FTW were collected and analyzed. The growth of plants in each system was also monitored, observing their general conditions. The chemical-physical characteristics of the pretreated domestic wastewater depended on the primary treatment installed. During the monitoring period we observed different reduction performance of the wetland sector in the three sites. In general, the wetland systems demonstrated the capacity to reduce TN, COD, BOD5 and Escherichia coli, whereas NO3-N and NH4-N removal was strictly influenced by the chemical conditions, in particular DO concentration, in the h-SSF and FTW. Vegetation (Phragmites australis, Alnus glutinosa and Salix eleagnos) was well established in the h-SSF as well as in the floating elements (Iris pseudacorus), although there were some signs of predation. FTW is a relatively novel wetland system, so the results obtained from this study can pave the way for the application of this technology.

Modelling assessment of carbon supply by different macrophytes for nitrogen removal in pilot vegetated mesocosms

The aim of this study was the evaluation of carbon supply by different macrophytes for nitrogen removal in constructed wetlands, using a dynamic numerical model previously developed by our work group to assess the results of a recently published meso-scale experiment. The experiment consisted of 12 mesocosms (five different macrophytes plus an unvegetated control, two cells each) drained once a week and immediately fed again until complete submersion with a solution of ammonium nitrate. To leave out any external carbon supply, no carbon substrate was added to the feed flux and no organic soil was included in the support media. The numerical simulations were obtained by calibration of the nitrification and denitrification processes driven by the alternate aerobic-anoxic phases generated by the weekly filling–emptying cycles. The carbon supplied by plants was demonstrated to be the main parameter affecting the denitrification rates observed in the experiments. It ranged in summer from 5.76 to 7.02 g/(m2 d), while the control accounted for 5.11 g/(m2 d). A winter test showed a 54% reduction of the summer supply of the same plant. The observed evapotranspiration rates were also simulated, and were shown to significantly affect the behaviour of the mesocosms planted with different species. Finally, the different vertical root-density distributions of the plants were found to play a relevant role in the development of nitrogen removal.