The aim of the MODUS technology is to create a highly oxidized natural covering of the contaminated sediment (bio-ox-capping) by oxygenating the deep water present above the sediment without perturbing it. This would greatly favor the colonization of animals and benthic microorganisms, which will permit a definitive return of life to the sea sediment [

4]. In order to prevent sediment perturbation, the technology here proposed would allow the contaminated sediments to be maintained unperturbed in situ while oxygenated water flows tangentially to it, as shown by our turbulence tests reported in

Figure 3 and

Figure 4. The experiments indicated that, even at the maximum possible water flow, no sediment resuspension was ever observed.

On the other hand,

Figure 5 and

Figure 6 show an interesting behavior of the mini-MODUS. First, the mini-MODUS appeared to work at very low levels of air flow [

12,

13,

14,

27,

28]; an air flow of 1 L min

^{−1} still produced a water flow of about 3 L min

^{−1}. Second, at the beginning, an increase in air flow produced a sharp linear increase [

14] of water flow (

Figure 5) and the induced water flow was systematically superior to the corresponding air flow (e.g., an air flow of 5 L min

^{−1} generates a water flow of about 7.5 L min

^{−1}) [

3,

13,

14,

27]. This would likely suggest that the dragging effect (water pulled by air) was very strong. A third point can be said on the fact that despite the initial sharp linear increase, a plateau was quickly reached, and beyond an air flow of about 11 L min

^{−1}, no increase of water flow above about 9 L min

^{−}1 was ever observed [

12,

13,

14]. All these represent fundamental aspects of the mini-MODUS’s behavior that would probably be crucial in the design of a larger scale MODUS (for example on “pilot-plant” scale). The consequence of the presence of the water flow plateau is that the residence time (

Figure 6) also experiences a horizontal segment beyond 11 L min

^{−1}. Indeed, from this air flow, the residence times do not decrease below 1.6 s.

The presence of the water flow plateau displayed in

Figure 5 should guarantee that sediment resuspension is excluded, even if air flow is increased beyond 25 L min

^{−1}. The existence of such a water flow plateau can probably be rationalized, assuming that at strong air flows, the air occupies a large part of the oxygenation reactor, leaving a smaller volume for the water: the air–water mixture will be composed mainly of air while resulting poor in water, and so the ensuing water flow will be lowered. On the other hand, there could also be a dragging effect and the compromise between these two forces could be the plateau (beyond ca. 11 L min

^{−1} of air flow) observed in the diagram. The consequent residence time plateau, from a practical point of view, means that for a certain specific geometry of the equipment and for given experimental conditions, an increase in the air flow does not produce a reduction of the residence time, for example, of polluted water. This is important because different residence times imply different contact times between air and water and therefore the possibility of having oxygen exchange between air and water: the presence of the horizontal segment assures that there will always be enough time for such an exchange. However, a better description of what happened in the aeration reactor will be provided by the oxygenation tests that were aimed to find the best oxygenation conditions. The three diagrams depicted in

Figure 7,

Figure 8 and

Figure 9 provide some glimpse on the mini-MODUS behavior at a deeper level. Assuming K

_{La} is linear within the considered air flow intervals, OC should also be linear [

3], despite more noise added to the OC with respect to K

_{La} due to C

_{s} variations as a consequence of temperature fluctuations. In the hypothesis of K

_{La} linearity, we can apply a linear regression to find the best fit, which would be y = m

_{1}x + q

_{1} where x = air flow and y = K

_{La}. Such a linear regression produced the following figures: m

_{1} = 0.0566 10

^{−4} min L

^{−1} s

^{−1} and q

_{1} = 1.5988 10

^{−4} s

^{−1}with R

_{1}^{2} = 0.9947. As m

_{1} and q

_{1} are independent from the air flow, we suggest that these parameters can be used to characterize a specific equipment once fixed with certain “standard conditions” (for example: tap water, 20 °C, 1 atm of atmospheric pressure, etc.). If we also apply the linear regression to OC, we obtain m

_{2} = 0.0843 10

^{−3} kg min h

^{−1} L

^{−1} and q

_{2} = 2.5394 10

^{−3} kg h

^{−1} with R

_{2}^{2} = 0.9884. On the other hand, while an air flow increase results in an increase in both K

_{La} and OC, vice versa the OE% decreases. Interestingly, similar to the residence time, OE% does not tend to zero for increasing air flows, but instead seems to reach a “plateau value”, this time beyond the air flow of ca. 25 L min

^{−1}. This is probably because the expression of OE is of the kind y = (m

_{2}x + q

_{2})/kx, where y = OE, m

_{2}x + q

_{2} = OC (in kg h

^{−1}), and kx = O

_{2}int (where k = 0.017957142 min kg L

^{−1} h

^{−1}, x = air flow in L min

^{−1}, and so kx will be expressed in kg h

^{−1}). Therefore, when x→∞, it is y→m

_{2}/k = 4.7 10

^{−3}, which is 0.47% (i.e., in theory OE% would tend asymptotically to be 0.47%). However, it is necessary to point out that OE% ≠ y = (m

_{2}x + q

_{2})/kx inasmuch, for example, for x→0 it is y→∞ while, obviously, OE% cannot overstep 100%. Therefore, a possible overlap between OE% and y = (m

_{2}x + q

_{2})/kx should be considered as limited to an air flow interval of 1–25 L min

^{−1} and not too far beyond it.