Desalination 215 (2007) 44–55 A special issue devoted to and inspired by WaT3R, MEDA WATER International Conference on Sustainable Water Management, Rational Water Use, Wastewater Treatment and Reuse, Marrakech, Morocco, 8–10 June 2006. 0011-9164/06/$– See front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.0000.00.000 Constructed wetlands for the Mediterranean countries: hybrid systems for water reuse and sustainable sanitation Fabio Masi a *, Nicola Martinuzzi b a Ambiente e Lavoro Toscana ONLUS, via Pier Capponi 9, Florence 50132, Italy Tel. +39-055-47 0729; Fax +39-055-47 5593; email: masi@altnet.it b IRIDRA Srl, via Lorenzo il Magnifico 70, Florence 50129, Italy Received 25 August 2006; revised accepted 18 November 2006 Abstract One of the main problems in adopting extensive treatment for wastewater purification in hot climate countries, when also the effluent reuse is aimed, is the high evapotranspiration rate. This factor can play a key role in reducing the water output, a desirable effect in some cases but completely adverse when water reuse is a primary resource for the area. Constructed wetlands have an higher evapotranspiration rate in comparison with ponds or lagoons but they also have the shortest hydraulic retention time (HRT) amongst the whole group of extensive treatment techniques. The water loss can also be minimised using a particular design and configuration of the constructed wetland system. The most powerful combinations seems to be the coupling of horizontal and vertical submerged flow beds, called hybrid systems, which performances are analysed in the present paper. In terms of overall performances the following mean removal rates were obtained: COD 94%, BOD 5 95%, total suspended solids 84%, NH 4 + 86%, total nitrogen 60%, total phosphorus 94%. Keywords: Constructed wetlands; Hybrid systems; Reed beds; Pathogens removal; Wastewater reuse 1. Introduction Constructed wetlands (CWs) can be subdivided into two main categories: surface-flow or sub- surface-flow design. In surface-flow wetlands (FWS) the wastewater flows through a shallow basin planted with emergent and submerged macrophytes. These kinds of system are mainly exploited for tertiary treatment or polishing stage and also in several cases of diffuse pollution. In subsurface flow or “Reed-bed” treatment systems (RBTS), the wetland is filled with gravel or sand or similar substrates, and the plants, most com- monly reeds (Phragmites australis or communis), grow rooted in the filling medium. The direction of the water flow provides the names of the two most diffused designs for RBTSs, the horizontal flow (HF) and vertical flow (VF) systems. *Corresponding author.