## Materials and Methods  
### Experimental Setup  
The experiments were performed in four parallel 1 m\({}^{3}\) cube-shaped intermediate bulk containers (named IBC A, B, C, and D) made of white translucent polyethylene and held within a tubular iron cage. The IBCs were kept open with an opened surface of 1m\({}^{2}\) and placed inside a barn located next to a CW treating the liquid fraction of piggery manure. The aeration pipes were installed at the bottom of three of the four IBCs for air supply. Aeration was provided with a membrane blower, type BibusSecoh JDK20, one for each aerated IBC. Each of the IBCs was filled up to ninety percent of their capacity with normal round expanded clay aggregates (Argex(r)). Their particle size was between 8 to 16 mm with a dry-weight density of 340 kg/m\({}^{3}\). An approximate volume of 400 L was filled with influent of the CW which was not renewed throughout the whole experiment. The different aeration rates were provided in each of the three IBCs and one was kept without aeration for comparison. When air was provided, the flux was 25 L/min. The aeration cycles were set in a way that IBC A was constantly aerated, whereas IBC B and C represented two intermittent aeration systems with two different aerated/non-aerated cycles every day. For IBC B, the intermittent aeration regime consisted of four hours with aeration followed by four hours without aeration. For IBC C, the intermittent aeration regime consisted of six hours with aeration followed by four hours without aeration. The IBC D served as a not-aerated control. The whole testing period had a duration of four months (June to October 2017). A schematic representation of the experimental setup is presented in Figure 1.  
Figure 1: Schematic representation of the operating batch mode intermediate bulk containers (IBCs) used to test the effect on inorganic (TN, NO\({}_{3}\)\({}^{-}\), NH\({}_{4}\)\({}^{+}\)) and organic (chemical oxygen demand (COD), biological oxygen demand (BOD)) chemical concentrations subjected to different aeration rates: (**a**) constant aeration, (**b**) 4 h period with aeration followed by 4 h without aeration, (**c**) 6 h period with aeration followed by 4 h without aeration, (**d**) absence of artificial aeration. Approximately 90% of each IBC capacity was filled with expanded clay and 400 L of influent wetland water. Three research questions were formulated considering the different aspects to assess during the experimental process. At the beginning or first experimental stage, it was hypothesised that ammonium volatilisation due to active aeration may be substantial. To test this effect, an additional solution of ammonium 15% was added to each IBC to reach an initial concentration of 200 mgNH4\({}^{+}\)-N/L. TN, NO3\({}^{-}\) and NH4\({}^{+}\) concentrations were determined from the samples collected at the top right and left corners, and from the centre of each container between 40 to 50 cm depth. The daily samples were collected during five consecutive days. Following this sequence, a six-week stabilisation period of the IBC systems was considered as appropriate to allow biofilm growth prior to proceeding with the second stage of the experiment. The constant and intermittent aeration regimes were kept during this six-week period. While testing a comparable experimental set-up, [PERSON] et al. [20] and [PERSON] et al. [4] considered a period of two months for the establishment and acclimatisation for microbial communities to populate the substrate particles. In the second stage of the experiment, the effect of aeration was evaluated considering the evolution of COD, BOD, TN, NO3-N and NH4\({}^{+}\)-N concentrations. The samples were collected at the same spots of each container on a regular basis twice a week during a period of two months. The third stage of the experiment considered the addition of an external carbon source (glucose) solution in each container. Its influence was tested on the denitrification process which was possibly affected by the continuous and intermittent aeration regimes.