Constructed wetlands offer promising solutions for controlling nutrient pollution in agricultural systems with relatively low costs and energy inputs. In mainly central and northern Italy, semi-natural and reconstructed Free-Water Surface Constructed Wetlands (FWS CWs) are designed to treat nonpoint-source pollution from agricultural catchments. However, their performance depends on system design and time of establishment. This paper evaluates the efficiency of a recently established FWS CW to remove nonpoint-source nutrient pollution due to agricultural drainage in the low-lying Venetian plain (NE Italy). The system was established in 2014 by creating five consecutive sub-basins vegetated with macrophytes to restore a semi-natural wetland, and later monitored in terms of water quality parameters and nutrients removal over three consecutive agricultural seasons (2014-2016). Total (TN) and nitrate (N-NO3) nitrogen concentrations showed peaks (16.37 and 15.31 mg l(-1) for TN and N-NO3, respectively) in the various sub-basins during spring 2015, associated with fertilisation of surrounding croplands and intense rain events. Performance improved over the three years, with increasing median removals of TN (33.3-49.0%) and N-NO3 (32.2-80.5%), corresponding to average mass of 1355 kg y(-1) and 1011 kg y(-1) for TN and N-NO3. Concentrations of ammonium (N-NH4) and orthophosphate (P-PO4) were generally low (<1 and <0.3 mg l(-1) for N-NH4 and P-PO4, respectively), with average yearly mass removals of 50 kg for N-NH4 and 9 kg for P-PO4. According to the overall treatment performance, the FWS CW could treat a total area of about 30 ha with a wetland/catchment ratio of 7%. However, we expect that treatment efficiency will increase as a result of bank stabilisation and improvement of the aquatic environment, together with increases in surface vegetation. (C) 2018 Elsevier B.V. All rights reserved.
Newly-established free water-surface constructed wetland to treat agricultural waters in the low-lying Venetian plain: Performance on nitrogen and phosphorus removal
nicola dal ferro
;Hend;maurizio borin
2018
Abstract
Constructed wetlands offer promising solutions for controlling nutrient pollution in agricultural systems with relatively low costs and energy inputs. In mainly central and northern Italy, semi-natural and reconstructed Free-Water Surface Constructed Wetlands (FWS CWs) are designed to treat nonpoint-source pollution from agricultural catchments. However, their performance depends on system design and time of establishment. This paper evaluates the efficiency of a recently established FWS CW to remove nonpoint-source nutrient pollution due to agricultural drainage in the low-lying Venetian plain (NE Italy). The system was established in 2014 by creating five consecutive sub-basins vegetated with macrophytes to restore a semi-natural wetland, and later monitored in terms of water quality parameters and nutrients removal over three consecutive agricultural seasons (2014-2016). Total (TN) and nitrate (N-NO3) nitrogen concentrations showed peaks (16.37 and 15.31 mg l(-1) for TN and N-NO3, respectively) in the various sub-basins during spring 2015, associated with fertilisation of surrounding croplands and intense rain events. Performance improved over the three years, with increasing median removals of TN (33.3-49.0%) and N-NO3 (32.2-80.5%), corresponding to average mass of 1355 kg y(-1) and 1011 kg y(-1) for TN and N-NO3. Concentrations of ammonium (N-NH4) and orthophosphate (P-PO4) were generally low (<1 and <0.3 mg l(-1) for N-NH4 and P-PO4, respectively), with average yearly mass removals of 50 kg for N-NH4 and 9 kg for P-PO4. According to the overall treatment performance, the FWS CW could treat a total area of about 30 ha with a wetland/catchment ratio of 7%. However, we expect that treatment efficiency will increase as a result of bank stabilisation and improvement of the aquatic environment, together with increases in surface vegetation. (C) 2018 Elsevier B.V. All rights reserved.
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