Ecological Engineering 41 (2012) 13–21 Contents lists available at SciVerse ScienceDirect Ecological Engineering j ourna l ho me page: www.elsevier.com/locate/ecoleng Removal of ionophoric antibiotics in free water surface constructed wetlands Syed Azfar Hussain, Shiv O. Prasher ∗ , Ramanbhai M. Patel Bioresource Engineering Dept., McGill University, Montreal 21111, Lakeshore Road, Ste. Anne de Bellevue, QC, Canada H9X 3V9 a r t i c l e i n f o Article history: Received 2 April 2011 Received in revised form 27 October 2011 Accepted 10 December 2011 Available online 3 February 2012 Keywords: Monensin Salinomycin Narasin Pharmaceuticals Free water surface wetlands Ionophores a b s t r a c t Pharmaceuticals are organic compounds that are being widely considered as emerging contaminants. Among pharmaceuticals used exclusively for veterinary purposes, ionophore group of compounds form a prominent class. Based on the usage and detected environmental concentrations, ionophores are consid- ered as high-risk compounds. This study was conducted to determine the removal efficiency of monensin, salinomycin and narasin in two free water surface constructed wetlands with different substrates: one with a sandy clay loam soil and another with a sandy soil. Three concentrations of each antibiotic in water were used. A significantly higher removal occurred with the sandy (vs sandy clay loam) soil. This enhanced removal was construed to be attained because water was able to infiltrate more in the sandy soil, provid- ing greater solute-to-substrate interaction. The correlations obtained for removal with parameters like oxygen-reduction potential, temperature and pH indicated that sorption and degradation processes could be working together in both soils. Among the three compounds, monensin and narasin were found to be, respectively, the most and least mobile. Removal efficiencies were significantly affected by the antibiotic concentration in the influent. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The ever-increasing demand for food and fiber has pushed agricultural industry toward using more and more organic and inorganic chemicals. These compounds are finding their way into fresh water resources, and potable waters. Concern on pollution by pharmaceuticals has grown after confirmation of their pres- ence and ability to pseudo-persist in the environment (Heberer et al., 2002). These low-level environmental concentrations have the ability to directly affect exposed biota (Glassmeyer et al., 2008); they can also instigate resistance in some bacteria that can poten- tially be transferred to pathogens (Srinivasan et al., 2008). On account of simultaneous presence of a wide variety of these com- pounds, there is also a possibility of additive or synergistic effect on the exposed environment (Hansen et al., 2009a). A recent survey across US reported the detection of drugs in the drinking water sup- plies of 24 major metropolitan, potentially affecting more than 13% of the country’s population (Donn et al., 2008). On account of their antimicrobial characteristics, antibiotics can also detrimentally affect pollutant specific bacterial strains thus increasing the persis- tence of such contaminants in the environment (Kim et al., 2011). The drugs found in the environment can be traced back to two sources: human consumption and veterinary usage. It is estimated ∗ Corresponding author. Tel.: +1 514 398 7775; fax: +1 514 398 8387. E-mail address: shiv.prasher@mcgill.ca (S.O. Prasher). that 75% of antibiotics administered to animals are not absorbed, and are excreted in waste (Chee-Sanford et al., 2009). Antimicro- bials used in the livestock industry have been detected in surface waters in Canada (Lissemore et al., 2006; Smyth et al., 2008), the USA (Watkinson et al., 2009), Europe (Feitosa-Felizzola and Chiron, 2009) and Asia (Managaki et al., 2007; Minh et al., 2009). The pre- dominant sources of these drugs are Concentrated Animal Farming Operations (CAFOs) and freshly manured agricultural soils (Pruden, 2009). Moreover, the possibility of direct leaching/runoff in high concentrations from manure stockpiles has also been reported (Dolliver and Gupta, 2008; Khan et al., 2008). Among pharmaceuticals used exclusively for veterinary pur- poses, ionophore group of compounds form a prominent class. Despite the fact that some studies have found these compounds to be somewhat susceptible to microbial degradation (Ramaswamy et al., 2010; Hussain et al., 2011b), based on the usage and detected environmental concentrations, ionophores are consid- ered as high risk compounds (Hansen et al., 2009b). Recent studies have detected these compounds in environmental matri- ces (Onesios et al., 2009 Watanabe et al., 2008). These compounds comprise of complex, high molecular weight molecules, derived from various streptomyces species. Among this group, monensin, salinomycin and narasin are the most commonly administered compounds. All three have been detected in environmental waters (Kim and Carlson, 2006). Only recently Hussain et al. (2011a) reported the removal efficiency of horizontal subsurface wet- lands for these three compounds. The molecular structures and 0925-8574/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ecoleng.2011.12.006