Constructed Wetlands as Green Systems for Urban Wastewater Management and Agricultural Reuse in Coastal Area

Coastal areas in Mediterranean regions are often characterized by water scarcity, with a large part of water resources exploited. The use of treated wastewater (TW) for agricultural activities can contribute to reduce this issue. This paper describes the performance of a hybrid constructed wetland (Hybrid-CW) used as a secondary stage of urban wastewater treatment plant and explores the effect of TW on horticultural crops. The Hybrid-CW, covering an area of 650 m2, consists of three natural treatment stages in series: i) a horizontal subsurface flow unit (HF1), ii) a vertical subsurface flow unit (VF) and iii) a horizontal subsurface flow unit (HF2). The experimental crop field (550 m2) is divided in two parallel systems, each one planted with lettuce (Lactuca var. Flavius) and zucchini (var. Sayonara.). These crops were irrigated with different type of water sources: treated wastewater from hybrid-CW and freshwater (FW). Even if the hybrid-CW operated at high hydraulic loading rate (HLR) about 2 time of the designed HLR, it efficiently removed BOD5, COD, TSS, TN and TP by 83 (±10) %, 80 (±9) % and 91 (±11) %, 44.8 (±18) %, 61 (±24) % respectively. The microbiological reduction rates, reported as Escherichia coli, were 3.2 (±1.6) Ulog. Crops irrigated with TW showed significant higher yields than those irrigated with conventional water resources.