2.2. Media composition and preparation

Columns were packed with solid support consisted of a mixture of peat (70% with 0.5 mm) and perlite (4–6 mm) at a 1:9 ratio. After characterization, the peat was dried at 103°C during 48 h to minimize bacterial activity. A layer of coarse gravel with 0.10 m of height was installed first at the bottom of the two columns and then these were packed with the media at a layer height of 1.30 m as described in Figure 1. A layer of perlite with 0.10 m of height was installed at the top of the two columns. For the conditioning, columns were fed slowly with tap water (1.5–2 h) in an ascending way to reach a maximum absorption capacity of water by peat [25], a good consistency of media and a resistance to compaction. The conditioning of columns removes also the retained air in the system.

### 2.3. Laboratory scale unit set up

Two mini-columns with 0.12 m of diameter and 0.20 m of height were set up as described in Figure 3 to simulate the top of pilot columns and to follow efficiency and parameters variability with time at the top of the pilot scale units.
