621 Environmental Technology, Vol. 28. pp 621-628 © Selper Ltd., 2007 PERFORMANCE AND COST COMPARISON OF A FWS AND A VSF CONSTRUCTED WETLAND SYSTEM V. A. TSIHRINTZIS 1 *, C. S. AKRATOS 1 , G. D. GIKAS 1 , D. KARAMOUZIS 2 AND A. N. ANGELAKIS 3 1 Laboratory of Ecological Engineering and Technology, Department of Environmental Engineering, Democritus University of Thrace, 67100 Xanthi, Greece 2 Hydraulics, Soil Science and Agricultural Engineering Division, Department of Agriculture, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece 3 Institute of Iraklio, National Foundation for Agricultural Research, P.O. Box 2229, 71307 Iraklio, Greece (Received 1 February 2006; Accepted 10 January 2007) ABSTRACT Two constructed wetland systems, treating domestic wastewater, are compared in terms of performance and costs. One is a free water surface (FWS) wetland system located in Pompia, Crete, south Greece, and the other one is a vertical subsurface flow (VSF) wetland system located in Gomati, Chalkidiki, north Greece. The FWS system is designed for 1200 p.e. Its construction cost was 305,000, and the capital, operation and maintenance cost was 22.07 p.e. -1 yr -1 or 0.50 m -3 of influent. The VSF system is designed for 1000 p.e. Its construction cost was 410,850, and the capital, operation and maintenance cost was 36.81 p.e. -1 yr -1 or 0.56 m -3 of influent. Both systems achieved high removal rates for BOD 5 , COD, TSS, TKN, phosphorus, TC, and FC, which makes them ideal for small communities in the Mediterranean region. Keywords: Free-water surface constructed wetland, vertical subsurface flow constructed wetland, treatment performance, construction cost; operation cost INTRODUCTION Constructed wetland (CW) wastewater treatment systems are considered more reliable compared to conventional systems [1], and are ideal technologies for small communities, due to their low construction, operation and maintenance costs, easy adaptation to the environment and limited generation of by-products [2,3]. One question however, is which is the optimum CW type (i.e., free-water surface (FWS), horizontal subsurface flow (HSF) or vertical subsurface flow (VSF) system) to use in a specific region, in terms of performance, costs, area requirements, and other factors. Most studies in the literature emphasize specific systems in terms of general performance [4-9]. Other studies examine the effect of various design parameters [10-13]. Comparisons of various CW types in the same region are limited (e.g., [14,15]). Construction and other cost data for CW systems are also limited (e.g., [16]). The necessity of pretreatment is an issue for discussion, since modified VSF designs in France operate successfully without pretreatment [17, 18]. Finally, small-scale on-site CW systems are now installed for single family use (e.g., [19]). The aim of this paper is to provide a perspective for applying constructed wetland technology in the Mediterranean regions and specifically in Greece. Descriptions, design considerations, construction cost, constituent removal performance, and operation and maintenance (O&M) costs of two constructed wetland systems (a FWS and a VSF) are presented. Both systems treat domestic wastewater and were designed for comparable treatment capacities. METHODS AND MATERIALS System Description Two constructed wetland systems treating domestic wastewater are compared in terms of costs and performance. One is a FWS wetland system located in Pompia, Crete, South Greece, and the other is a VSF wetland system located in Gomati, Chalkidiki, Macedonia, North Greece.