title: Assessment of uncertainty in constructed wetland treatment performance and load estimation methods.
abstract: Constructed wetlands (CWs) are commonly established to reduce pollution load from different sources. In environmental permits, the load remaining after CW purification is typically estimated through concentration and flow measurements. This load monitoring is often carried out using long water quality sampling intervals, which causes uncertainty in load estimation. In this study, a large suspended solids (SSs) and dissolved organic carbon (DOC) dataset was used to quantify the uncertainty in load estimation at the inlet and outlet of a CW with different sampling frequencies (sampling every 1, 2, 3 or 4 weeks). A method to reduce the uncertainty by dividing the CW flow duration curve (FDC) into four equal categories and assigning mean/median concentration for each category according to the measured concentrations was also tested. The results showed that estimated SS load was associated with considerable uncertainty and that this uncertainty increased with lower sampling frequency. The FDC method was able to decrease the uncertainty, but much still remained, especially when concentrations of the measured variable showed great variation. In such cases, sensor technology might be a feasible option for further reducing the uncertainty.
authors.affiliation: Water Resources and Environmental Engineering Research Group, University of Oulu, P.O. Box 4300, FI-90014, Oulu, Finland. riku.eskelinen@oulu.fi.|Thule Institute, P.O. Box 7300, FI-90014, Oulu, Finland. riku.eskelinen@oulu.fi.
authors.forename: Riku
authors.initials: R
authors.lastname: Eskelinen
authors.affiliation: Water Resources and Environmental Engineering Research Group, University of Oulu, P.O. Box 4300, FI-90014, Oulu, Finland.
authors.forename: Anna-Kaisa
authors.initials: AK
authors.lastname: Ronkanen
authors.affiliation: Water Resources and Environmental Engineering Research Group, University of Oulu, P.O. Box 4300, FI-90014, Oulu, Finland.
authors.forename: Hannu
authors.initials: H
authors.lastname: Marttila
authors.affiliation: Water Resources and Environmental Engineering Research Group, University of Oulu, P.O. Box 4300, FI-90014, Oulu, Finland.
authors.forename: Bjørn
authors.initials: B
authors.lastname: Kløve
mesh_terms: D004784:Environmental Monitoring; D013223:Statistics as Topic; D035501:Uncertainty; D014876:Water Pollution / Q000032:analysis*; D018508:Water Purification; D060753:Water Quality; D053833:Wetlands
keywords: Constructed wetland; Load estimation; Sampling frequency; Uncertainty estimation