Constructed wetlands as nature-based solution for sustainable wastewater management in urban areas: a critical assessment by experimental studies and literature

In urban areas, constructed wetland systems (CWS) have been recognized as one of the most valid technologies for sustainable wastewater management. They represent green infrastructure and provide solutions to treatment of wastewaters that cities and peri-urban areas produce in large amount. In particular, CWS offer the advantages of wastewater reuse for parklands irrigation, water storage and peak-flow attenuation, control of stormwater runoff, nutrient cycling and uptake, heavy metals sequestration, removal of organic compounds. In greener cities, these systems have the potential to perform not just hydrological and wastewater treatment functions, but also urban design and ecological aspects as demonstrated by numerous applications around the world. CWS, in fact, can function as urban wildlife sites, educational or recreational facilities, landscape engineering and ecological areas. The aim of this paper was to highlight the potential functionality of CWS in urban areas by a critical assessment of two experimental studies and literature. In particular, the two studies were carried out in Sicily (Italy) in order to evaluate: i) the pollutant removal efficiency of two CWS to treat urban wastewater and first-flush stormwater; ii) the reuse of treated wastewater for irrigation of plants. The results confirm that CWS are efficient in the treatment and reuse of wastewater for irrigation purposes in modern cities. Furthermore, CWS showed very high organic pollutant removal and a good efficiency in reducing excess of nutrients and trace metals, highlighting their important role in the treatment of stormwater in urban areas.