Ecological Engineering 47 (2012) 36–43 Contents lists available at SciVerse ScienceDirect Ecological Engineering j o ur nal homep age : www.elsevier.com/locate/ecoleng Wetland plants, micro-organisms and enzymatic activities interrelations in treating N polluted water Michela Salvato a,∗ , Maurizio Borin a , Serena Doni b , Cristina Macci b , Brunello Ceccanti b , Sara Marinari c , Grazia Masciandaro b a Dipartimento di Agronomia Animali Alimenti Risorse naturali e Ambiente (DAFNAE), Università degli Studi di Padova, Viale dell’Università 16, 35020 Legnaro, Padova, Italy b Istituto per lo Studio degli Ecosistemi, Centro Nazionale delle Ricerche, Via Moruzzi 1, 56124 Pisa, Italy c Dipartimento di Agrobiologia e Agrochimica, Università degli studi della Tuscia, Via S Camillo de Lellis, Viterbo, Italy a r t i c l e i n f o Article history: Received 9 December 2011 Received in revised form 12 June 2012 Accepted 23 June 2012 Keywords: Macrophytes N treatment Microbial population Enzymatic activity Root system a b s t r a c t This study compared the efficiency of five emergent plant species (Carex elata All., Juncus effusus L., Typhoides arundinacea (L.) Moench var. picta, Phragmites australis (Cav.) Trin. and Typha latifolia L.) used for the decontamination of nitrogen polluted water at mesoscale level. The correlations between N removal and microorganisms content and activity on root and gravel surfaces were also evaluated in order to broaden the knowledge about water purification processes. The experiment was conducted in plastic tanks for two years (2008–2009), performing drying/wetting application cycles with NH 4 NO 3 solution. At the end of the experiment, root and gravel samples were collected from each tank for the mea- surement in aqueous extracts of total cultivable microbial population and Pseudomonas genus, and -glucosidase, chitinase, phosphatase and leucine aminopeptidase activities; other base chemical analy- ses (electrical conductivity, water soluble carbon, nitrate and ammonia) were conducted. The production of bio-available root exudates was evaluated though the quantification of water soluble carbon (WSC) in root and gravel washing water. WSC seems to support the plant denitrification activity because T. arundinacea and Ph. australis systems, which showed the highest WSC content, achieved the highest denitrification percentages (37% and 34%, respectively). In these plant systems the higher cul- tivable microbial population and rhizospheric hydrolytic activity found were probably induced by the high content of soluble organic substrates that derived from root turnover and root exudation, without addition of any other carbon source. The establishment of this active micro-environment (rhizo-biospace) has high ecological significance due to the role played by microbial activity in the nutrient cycles and is of great importance when choosing suitable plant species for wastewater treatment. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Nitrogen is one of the most important nutrients for organisms. The excessive accumulation of nitrogen discharged into water due to urbanization and intensive farming can cause serious ecological problems. Ammonia, in particular, is an undesirable constituent of many wastewaters because of its toxicity to fish and its signif- icant, microbial-induced, oxygen demand on the receiving water body (Camargo and Alonso, 2006). In addition, ammonia and nitrate ∗ Corresponding author. Tel.: +39 0498272838; fax: +39 0498272839. E-mail addresses: michela.salvato@unipd.it (M. Salvato), maurizio.borin@unipd.it (M. Borin), serena.doni@ise.cnr.it (S. Doni), cristina.macci@ise.cnr.it (C. Macci), brunello.ceccanti@ise.cnr.it (B. Ceccanti), marinari@unitus.it (S. Marinari), grazia.masciandaro@ise.cnr.it (G. Masciandaro). stimulate biological productivity, which can ultimately lead to biomass decay and dissolved oxygen depletion (eutrophication process). Constructed wetlands (CWs) are nowadays a low cost, efficient wastewater treatment and widely employed technology to treat agricultural, municipal and industrial wastewaters (Kadlec and Wallace, 2008). Treatment behaviour in CWs is often considered to be a fig- urative black-box (Rousseau et al., 2004) where the interactions between vegetation, water and microorganisms are little known (Toscano et al., 2009). The plants have many important functions in nitrogen removal in CWs, such as direct uptake of nitrogen for their growth, providing a surface and a carbon source for the growth of microbial communi- ties, transferring oxygen from air to the medium, decreasing water 0925-8574/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ecoleng.2012.06.033