Sustainability indicators of subsurface flow constructed wetlands in Portuguese small communities

Abstract

The discharge of untreated domestic wastewater in the receiving waters creates a negative and environmental impact, inversely proportional to its autodepuration ability. Conventional wastewater treatment plants involve large capital investments and operating costs, and could be economically unsustainable for small-medium communities. So, constructed wetlands as natural low-cost systems can be an appropriate alternative, because they require low maintenance, give rise to good performances and provide a natural appearance. This work presents a synthesis of data obtained through an extensive survey performed in twenty Portuguese constructed wetlands utilities. Based on this information, some sustainable indicators and removal pollutant efficiencies were calculated. Besides identifying the main operational problems observed, it was also possible to detect inadequate monitoring procedures, aiming, with some proposed corrections, to improve the performance of these low-cost wastewater treatment utilities. The results obtained in this work encourage the development of future studies to increase the performance of these wastewater systems based on a better knowledge of the influence of hydraulic parameters, like flow, retention time and hydraulic application rate, in the pollutants removal efficiencies.