Massoud et al., 2009), the technologies should be low-cost, energy saving, low-maintenance, effective, and stable (Aiyuk et al., 2004;Heistad et al., 2006).Typically, decentralized on-site wastewater management for an individual home consists of a septic tank for pretreatment and an effluent dispersal system (Brix and Arias, 2005; Dawes and Goonetilleke, 2003; Leverenz et al., 2010). For nitrogen and phosphorus removal, the treatments mainly include Constructed Wetlands (CW), Intermittent Sand Filters (ISF), and Land Treatment Systems (LTS) (Healy et al., 2007; Massoud et al., 2009; Tanner et al., 2012). However, following population growth and urbanization, the cost and availability of land is becoming a restrictive factor that demands efficiency in terms of facility area (Aiyuk et al., 2004; Parkinson and Tayler, 2003; Sevda et al., 2013). The Vertical Flow CW (VFCW) promises a good alternative that satisfies the aforementioned requirements well (Brix and Arias, 2005). It was reported the most common design in France was the two-stage VFCW, which accepted raw sewage intermittently in the first stage mainly with coarse gravel and fulfilled the nitrification in the second stage with much finer media. Such systems, if well designed, can achieve an outlet level of 60mgL−1 in COD, 15mgL−1 in SS and 8mg L−1 in TKN with an area of 2–2.5m2 PE−1 (person equivalent) (Molle et al., 2005), less than official guidelines of 3.2m2 PE−1 by the Danish Ministry of Environment for the on-site treatment of domestic sewage (Brix and Arias, 2005).
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