Monitoring of Iron absorbtion using a constructed wetland pilot plant with an hybrid layout.

The main purpose of this study was strictly focused on the treatment of iron pollution present in an artificial wastewater (obtained starting from iron sulfate heptahydrate) by the use of constructed wetland system. The effect of different tanks technologies (vertical and horizontal subsurface flow), bedding material, and plant species was also investigated. A pilot-scale study was conducted on an hybrid layout CW system operated in vertical and horizontal mode. Two vertical systems differed from each other with their bedding material and planted with different species (Juncus and Typha Latifolia). Also one horizontal system, filled with different substrate and planted with Papyrus, was used after the two vertical tanks. The CW was designed to work as an hybrid system where the flow, of 50 l/day, crossed alternately from the two vertical tanks and then to the horizontal one. The hydraulic retention time was set equal to about 4 days and the Iron concentration in the inlet was 50mg/l. The test was designed to use batch feeding inside the system as a tank of 1000l was initially filled with 490l of water and 25g of iron sulfate diluted in 10l of water. After ten days of operation the inlet tank was refill again to restart another feeding phase. The test was conducted during two years of efficiency monitoring. Both physical and chemical parameters were collected with a multiparameters probe three times a week at three different sites of the system, in order to had sufficient and representative data. To determine the abatement of the initial concentration of iron in the CW system were done different samplings at the exit of each tanks (VF1, VF2 abd HF). The target to the CW system was provided from the Italian legislation (Legislative Decree 152/2006) for wastewater discharges into surface water bodies and drains. Concentration based on the best removal efficiencies for VF1, VF2 and HF were Iron 87,9%, 91%, 12,2% and a total removal efficiency of 90,7%.