title: Enhancement of total nitrogen removal through effluent recirculation and fate of PPCPs in a hybrid constructed wetland system treating urban wastewater.
abstract: The effect of effluent recirculation on the removal of total nitrogen (TN) and eight pharmaceuticals and personal care products (PPCPs) was evaluated during 9months in an experimental hybrid constructed wetland (CW) system applied in the treatment of urban wastewater. An Imhoff tank was followed by three stages of CWs (two 1.5-m2vertical subsurface flow (VF) beds alternating feed-rest cycles, a 2-m2horizontal (HF) and a 2-m2free water surface (FWS) wetland in series). A fraction of the final effluent was recycled back to the Imhoff tank with a recirculation rate of 50% (hydraulic loading rate=0.37md-1). The system's performance varied throughout the study. In Period I (summer) consistently high load removal efficiencies of TN (89±5%) and a removal rate of 6.6±1.4gTNm-2d-1were exhibited. In Period II (fall), the poor performance of the FWS during the senescence of macrophytes caused a large increase in organic matter, solids and nutrient concentrations, drastically deteriorating water quality. The determination of PPCPs was conducted during this period. Recalcitrant compounds, namely sulfamethoxazole, carbamazapine, TCEP and sucralose were negligibly removed in all CWs. However, noteworthy was the ≈30% removal of sucralose in the VF wetland. Caffeine (80%) and fluoxetine (27%) showed similar elimination rates in both VF and HF units, whereas trimethoprim and DEET were significantly better removed in the VF than in the HF. The concentration of the four latter compounds showed a severe increase in the FWS, indicating possible desorption from the sediment/biomass during adverse conditions. Harvesting of the aboveground biomass in this unit returned the system's performance back to normality (Period III), achieving 77±7% TN removal despite the winter season, proving effluent recirculation as an effective strategy for TN removal in hybrid CW systems when stringent restrictions are in place.
authors.affiliation: GEMMA- Environmental Engineering and Microbiology Research Group, Department of Civil and Environmental Engineering, Universitat Politècnica de Catalunya-BarcelonaTech, c/ Jordi Girona, 1-3, Building D1, E-08034 Barcelona, Spain; ICRA, Catalan Institute for Water Research, Scientific and Technological Park of the University of Girona, Emili Grahit, 101, E-17003 Girona, Spain. Electronic address: cavila@icra.cat.
authors.forename: Cristina
authors.initials: C
authors.lastname: Ávila
authors.affiliation: GESAD-Decentralized Sanitation Research Group, Department of Sanitary and Environmental Engineering, Federal University of Santa Catarina, Trindade, Florianópolis, Santa Caterina CEP 88040-900, Brazil.
authors.forename: Catiane
authors.initials: C
authors.lastname: Pelissari
authors.affiliation: GESAD-Decentralized Sanitation Research Group, Department of Sanitary and Environmental Engineering, Federal University of Santa Catarina, Trindade, Florianópolis, Santa Caterina CEP 88040-900, Brazil.
authors.forename: Pablo H
authors.initials: PH
authors.lastname: Sezerino
authors.affiliation: Department of Civil Engineering and Architecture, University of Catania, Viale A. Doria 6, 95125 Catania, Italy.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Sgroi
authors.affiliation: Department of Civil Engineering and Architecture, University of Catania, Viale A. Doria 6, 95125 Catania, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Roccaro
authors.affiliation: GEMMA- Environmental Engineering and Microbiology Research Group, Department of Civil and Environmental Engineering, Universitat Politècnica de Catalunya-BarcelonaTech, c/ Jordi Girona, 1-3, Building D1, E-08034 Barcelona, Spain.
authors.forename: Joan
authors.initials: J
authors.lastname: García
keywords: Desorption; Emerging organic contaminant; Pharmaceuticals and personal care products; Plant decay; Sucralose; Treatment wetland