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An assessment of the performance of municipal constructed wetlands in Ireland.

Hickey, Anthony, Arnscheidt, Joerg, Joyce, E, o'Toole, J, Galvin, G, o' Callaghan, M, Conroy, K, Killian, D, Shryane, T, Hughes, F and Kavanagh, E (2018) An assessment of the performance of municipal constructed wetlands in Ireland. Journal of Environmental Management, 210 . pp. 263-272. [Journal article]

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DOI: 10.1016/j.jenvman.2017.12.079

Abstract

While performance assessments of constructed wetlands sites around the world have appraised their capacity for effective removal of organics, a large variance remains in these sites' reported ability to retain nutrients, which appears to depend on differences in design, operation and climate factors. Nutrient retention is a very important objective for constructed wetlands, to avoid eutrophication of aquatic environments receiving their effluents. This study assessed the performance of constructed wetlands in terms of nutrient retention and associated parameters under the humid conditions of Ireland's temperate maritime climate. A review of the performance of 52 constructed wetland sites from 17 local authorities aimed to identify the best performing types of constructed wetlands and the treatment factors determining successful compliance with environmental standards. Data analysis compared effluent results from constructed wetlands with secondary free surface flow or tertiary horizontal subsurface flow, hybrid systems and integrated constructed wetlands with those from small-scale mechanical wastewater treatment plants of the same size class. Nutrient concentrations in effluents of constructed wetlands were negatively correlated (p < .01) with specific area, i.e. the ratio of surface area and population equivalents. The latest generation of integrated constructed wetlands, which had applied design guidelines issued by the Department of the Environment, performed best. Storm management design features improved treatment performance of constructed wetlands significantly (p < .05) for total suspended solids concentrations and exceedance frequency of limit values for total nitrogen. Mechanical wastewater treatment plants, secondary free surface water and tertiary horizontal subsurface flow wetlands showed a very large variance in effluent concentrations for organic and nutrient parameters. E. coli numbers in effluents were lowest for integrated constructed wetlands with an arithmetic mean of 89 MPN/100 ml. Despite Ireland's humid climate, some constructed wetland sites achieved long or frequent periods of zero effluent discharge and thus did not transfer any waterborne pollution to their receptors during these periods.

Item Type:Journal article
Keywords:Constructed wetlands; wastewater treatment; water quality; phosphorus; nitrogen; storm management; specific area
Faculties and Schools:Faculty of Life and Health Sciences > School of Geography and Environmental Sciences
Faculty of Life and Health Sciences
Research Institutes and Groups:Environmental Sciences Research Institute
Environmental Sciences Research Institute > Freshwater Sciences
ID Code:39460
Deposited By: Dr Joerg Arnscheidt
Deposited On:23 Mar 2018 17:42
Last Modified:23 Mar 2018 17:42

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