title: Effect of plant species on water quality at the outlet of a sludge treatment wetland.
abstract: Sludge treatment wetlands are mainly used to reduce the volume of activated sludge, and the pollutants at the outlet are generally returned to the wastewater treatment plant. However, in cases where sludges are produced far from treatment plants not only must the sludge be treated, but the discharge of pollutants into the surrounding environment must also be limited. The aim of this study was to evaluate the efficiency of different plant species in optimising pollutant removal in a decentralised sludge treatment wetland. In addition, a new system design was assessed, in which the wetland was not completely drained, and a saturated layer was created using an overflow. The experimental setup consisted of 16 mesocosms in total, planted with monocultures of Phragmites australis, Typha angustifolia and Scirpus fluviatilis, and unplanted controls, each in four replicates. The experiment was conducted during the third summer of operation after setup. The system was fed with highly concentrated fish farm sludge at a load of 30 kg of total solids m(-2) yr(-1). Results showed that such wetlands were highly efficient, with removal rates between 94% and 99% for most pollutants. Planted systems generally outperformed the unplanted control, with a significantly lower mass of pollutants at the outlet of the sludge treatment wetland planted with Phragmites, followed by those with Typha and then Scirpus. The distinct influence of plant species on pollution removal was explained by the sequestration of nitrogen and phosphorus in plant tissues and by the rhizosphere effect, which enhance the biodegradation of organic matter, allowed the nitrification process and created redox conditions favourable to the sorption of phosphorus. Filtration and evapotranspiration rates played a major role in limiting the discharge of pollutants, and the impact was enhanced by the fact that the sludge treatment wetland was not completely drained.
authors: Institut de Recherche en Biologie Végétale, Département de Sciences Biologiques, Université de Montréal, 4101 Sherbrooke Est, Montréal, Québec, H1X 2B2 Canada.
authors: Vincent
authors: V
authors: Gagnon
authors: Florent
authors: F
authors: Chazarenc
authors: Margit
authors: M
authors: Kõiv
authors: Jacques
authors: J
authors: Brisson
mesh_terms: D000704:Analysis of Variance; D017756:Aquaculture; D018533:Biomass; D029785:Cyperaceae / Q000378:metabolism; D006109:Poaceae / Q000378:metabolism; D012722:Sewage / Q000032:analysis*; D032401:Typhaceae / Q000378:metabolism; D014865:Waste Disposal, Fluid / Q000379:methods*; D014870:Water Loss, Insensible / Q000502:physiology; D014874:Water Pollutants, Chemical / Q000493:pharmacokinetics*; D060753:Water Quality / Q000592:standards*; D053833:Wetlands
chemical_list: D012722:Sewage; D014874:Water Pollutants, Chemical