Plant species for floating treatment wetlands: A decade of experiments in North Italy

Floating treatment wetlands (FTWs) represent a recent system within the family of surface flow wetlands, able to directly treat various types of waste waters in natural or artificial water bodies. In these conditions, traditional non-floating macrophytes, installed in self-buoyantmats, hydroponically expand their root systemsin the wastewater, interacting with a rich microbial biodiversity and thereby removing different pollutants. This study aimed to evaluate the growth performances of 5 plant species installed in different FTWs after ten years of research conducted in North Italy: Phragmites australis, Iris pseudacorus, Typha latifolia, Carex spp. and Lythrum salicaria. During the entire experimental period, above-mat biomass production varied from 46.7 g m(-2) (L. salicaria) to 1466.0 g m(-2) (T. latifolia), whereas below-mat biomass production ranged between 205.7 g m(-2) (L. salicaria) and 4331.1 g m(-2) (P. australis). Both shoot height and root length assumed the highest values for T. latifolia (189.0 cm and 59.3 cm, respectively), the lowest for L. salicaria (42.3 cm and 35.1 cm, respectively). All plant species increased both above- and below-mat biomass productions over consecutive growing seasons through horizontal colonization of the floating mats, although not always significantly. Moreover, the growth of I. pseudacorus, P. australis and T. latifolia was significantly influenced by wastewater physico-chemical composition, exhibiting species-specific behavior. In general, all species showed a good aptitude to survive in hydroponic conditions both during the growing season and the winter, even though in a few cases the survival of I. pseudacorus and P. australis was strongly reduced by alien predators (Myocastor coypus) that badly damaged plant aerial tissues. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Floating treatment wetlands (FTWs) are a new system within surface flow wetlands family that can directly treat various waste waters in natural or artificial water bodies. This study evaluated the growth performances of 5 plant species installed in different FTWs after ten years of research conducted in North Italy, showing all species gradually increased above- and below-mat biomass productions, although not always significantly. The growth of certain species was significantly influenced by wastewater physico-chemical composition, while some were damaged by alien predators.