Design of a constructed wetland for wastewater treatment in a Sicilian town and environmental evaluation using the emergy analysis

This study examines and evaluates, by means of the emergy analysis, the use of environmental resources for wastewater treatment in a Sicilian town. A traditional wastewater treatment plant coupled with a surface flow constructed wetland was considered for water purification. The surface area of the wetland was calculated by using a first order plug flow kinetic model; the area's value was a necessary parameter for the application of the emergy analysis. Water is part of the natural capital but, as water is processed through purification processes for city use, there are additional emergy and money values added. In the present application, the additional emergy value of water purification was calculated. The purpose of the analysis was to determine whether or not the installation of a constructed wetland on a Sicilian wastewater treatment plant may result in monetary savings and benefit the environment. The analysis done here shows that the proposed design not only results in savings by reducing electricity consumption, but also reduces pressure on the local environment by providing the option of recycling clean water. Furthermore, the emergy analysis which uses inputs both from natural ecosystems and the human economy, allows a quantitative evaluation of the environmental savings due to water reuse as well as the environmental impact due to the wastewater treatment process.