## 4 Results and Discussion
\begin{table}
\begin{tabular}{l c c c} \hline \hline \multirow{2}{*}{**Type/Model**} & **O\({}_{2}\)—NBs** & **O\({}_{2}\)—NBs** & **O\({}_{2}\)—NBs** \\  & **(mg/L)** & **(mg/min)** & **(mg/min/W)** \\ \hline
1: Moleaer Kingfisher & 0.15 * & 21 & 0.019 \\ \hline
2: Acriti Turbiti 727 & 0.2 **\(\pm\)** 0.04 & 10 \(\pm\) 3 & 0.017 \(\pm\) 0.005 \\ \hline
3V: AquaB In-line Tubular Pipe (Venturi) & 2.15 *** \(\pm\) 0.35 & 130 \(\pm\) 25 & 0.46 \(\pm\) 0.08 \\ \hline
3C: AquaB In-line Tubular Pipe (Air Comp.) & 2.85 *** \(\pm\) 0.4 & 285 \(\pm\) 40 & 0.77 \(\pm\) 0.12 \\ \hline
4V: AquaB Radial Vortex (Venturi) & 5.45 *** \(\pm\) 1.0 & 980 \(\pm\) 140 & 1.72 \(\pm\) 0.2 \\ \hline
4C: AquaB Radial Vortex (Air Comp.) & 7.2 *** \(\pm\) 1.1 & 1730 \(\pm\) 210 & 2.62 \(\pm\) 0.29 \\ \hline
5: Anzai Porous Membrane & 0.08 * & 2 & 0.007 \\ \hline
3V: AquaB In-line (Off-Grid, incl. P-drop) & 1.0 *** \(\pm\) 0.2 & 10 \(\pm\) 2 & 0.16 \(\pm\) 0.016 \\ \hline
3V: AquaB In-line (Off-Grid, excl. P-drop) & 1.0 *** \(\pm\) 0.2 & 10 \(\pm\) 2 & 1.67 \(\pm\) 0.16 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: O\({}_{2}\)-in-NB-form mass estimate (mg/L) and in mg/min, given the water flowrate, and normalised to mg/J. The number of asterisks shows the number of successful detections of nanobubbles out of three attempts. \begin{table}
\begin{tabular}{l c c c} \hline \hline \multirow{2}{*}{**Type/Model**} & **DO Boost** & **Overall DO Boost** & **Negative pH** \\  & **(mg/L)** & **per Watt (mg/W)** & **Shift** \\ \hline
1: Moleaer Kingfisher & 3.1 \(\pm\) 0.2 & 0.4 \(\pm\) 0.03 & 0.07 \(\pm\) 0.01 \\ \hline
2: Acriti Turbiti 727 & 3.4 \(\pm\) 0.2 & 0.29 \(\pm\) 0.025 & 0.08 \(\pm\) 0.01 \\ \hline
3V: AquaB In-line Tubular Pipe (Venturi) & 3.6 \(\pm\) 0.25 & 0.77 \(\pm\) 0.06 & 0.13 \(\pm\) 0.01 \\ \hline
3C: AquaB In-line Tubular Pipe (Air Comp.) & 4.3 \(\pm\) 0.3 & 1.16 \(\pm\) 0.1 & 0.16 \(\pm\) 0.01 \\ \hline
4V: AquaB Radial Vortex (Venturi) & 4.5 \(\pm\) 0.3 & 1.42 \(\pm\) 0.12 & 0.21 \(\pm\) 0.01 \\ \hline
4C: AquaB Radial Vortex (Air Comp.) & 5.2 \(\pm\) 0.35 & 1.89 \(\pm\) 0.14 & 0.24 \(\pm\) 0.01 \\ \hline
5: Anzai Porous Membrane & 1.6 \(\pm\) 0.1 & 0.14 \(\pm\) 0.01 & 0.06 \(\pm\) 0.01 \\ \hline
3V: AquaB In-line (Off-Grid, incl. P-drop) & 2.4 \(\pm\) 0.2 & 0.4 \(\pm\) 0.03 & 0.1 \(\pm\) 0.012 \\ \hline
3V: AquaB In-line (Off-Grid, excl. P-drop) & 2.4 \(\pm\) 0.2 & 4 \(\pm\) 0.3 & 0.1 \(\pm\) 0.012 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: DO boost levels (mg/L) at mid-range water flowrates and normalised to power. In terms of the level of boost in DO and pH shift arising from use of the flow-based NB generators, this is summarised in Table 5. It is important to note that DO probes do not measure directly the presence of NBs per se: rather, over time, the rate of NB release into the classically dissolved DO phase can lead to an indirect and rough assessment of the mass in NB form, bearing in mind the prevailing chemical and/or biological oxygen demands (which are low in the present heavily filtered municipal tap-water) [30]. Of course, there are more direct measurements of the mass concentration of the flow-generated nanophase in Table 4--which may underestimate more severely the lower levels of mechanically generated NBs' overall mass due to systematic underestimation measurement errors in headspace gas. Even so, bearing in mind this important note and qualifying caveat, the greater NB mass and energy efficiency in NB generation via the electric-field approach is noted, which passes ANOVA analysis at the 99% confidence level. The greater negative pH shift is also noted for the electric-field approach (owing, in part, to greater levels of nano-carbonation) [10].