## 4 Results and Discussion  
The DLS-determined NB populations taken directly after air-fed flow are provided below in Table 2. This was an average over three measurements, although Moleaer (1) and Anzai (5) did not register above the NB detection threshold in all cases; the number of asterisks beside the relevant population determine the number of times a NB population could actually be determined. In the case of the AquaB radial-vortex approach operated in air-compressor mode (4C), similar results were obtained via independent-party measurements [40]. \begin{table}
\begin{tabular}{l c c c} \hline \hline \multicolumn{1}{c}{**Type/Model**} & **Zetasizer Pro** & **Nanosight Pro** & **Power Draw (W)** \\ \hline
1: Moleaer Kingfisher & 4.82 * & 3.26 * & 1085 \\ \hline
2: Acniti Turbiti 727 & 6.5 *** \(\pm\) 2.9 & 4.1 ** \(\pm\) 1.1 & 585 \\ \hline
3V: AquaB In-line Tubular Pipe (Venturi) & 43 *** \(\pm\) 9 & 32 *** \(\pm\) 5 & 280 \\ \hline
3C: AquaB In-line Tubular Pipe (Air Comp.) & 71 *** \(\pm\) 11 & 42 *** \(\pm\) 7 & 370 \\ \hline
4V: AquaB Radial Vortex (Venturi) & 88 *** \(\pm\) 13 & 71 *** \(\pm\) 8 & 570 \\ \hline
4C: AquaB Radial Vortex (Air Comp.) & 110 *** \(\pm\) 18 & 94 *** \(\pm\) 11 & 660 \\ \hline
5: Anzai Porous Membrane & 1.22 * & 1.03 * & 290 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: NB populations (\(\times 10^{6}\) NBs per mL) and power from air-fed water-flow operation; AquaB is in both Venturi and air-compressor modes. The number of asterisks shows the number of successful detections of nanobubbles out of three attempts. If there is only one measurement of three (***), an uncertainty cannot be measured, as, by definition, a standard deviation cannot be computed under the circumstance of only a single viable measurement. Of course, it is possible to run the in-line AquaB units (3) without a water pump at lower water flowrates, on the order of 8-15 lpm, characteristic of domestic or light industrial municipal tap-water supply at \(\sim\)0.5 bar g delivery pressure. In that case, if one ignores the local water-pumping cost (that is now borne instead by the mains-water-providing utility, or the upstream water provider in general), and uses a Venturi arrangement (3V), the power draw borne by the end user operating the in-line AquaB NB generator is as little as \(\sim\)4-8 W (i.e., in essence, the overhead of AC-to-DC conversion)--cf. Table 3.  
It is clear that the greater level of internal flow turbulence inside the various NB generators promotes a greater level of macro- and mesobubble formation, as is evident from turbidity observations. In the case of AquaB electrostriction generators, this can also be seen, although to less effect, given that there appears to be a higher conversion of such larger bubbles into NB form (vide infra). It is also clear that there is a systematically higher population using the Zetasizer approach compared to Nanosight, with a greater level of uncertainty therein; the different light-scattering approaches render NTA of the Nanosight approach arguably more consistent and conservative, albeit with the 35 nm threshold in the case of NTA often underestimating the population--more particularly so for smaller AquaB NBs. The typical NB diameters, when detected, were \(\sim\)70-90 nm for AquaB (3 and 4), 75-95 nm for Anzai (5) and Aniti (2), and 80 to 105 nm for Moleaer (1). Coupled with higher AquaB NB populations, the slightly smaller size of the AquaB-generated NBs boosts oxygen-transfer efficiency with a superior surface-area-to-volume ratio (cf. Figure 1, top right, for a visual comparison of different bubble sizes in the sense of surface area to volume). Greater internal flow path turbulence at higher water and air flowrates can also, in the case of AquaB flow units, boost the NB population in non-linear proportion to the water and air flows and the power incurred in the air and water flows (whether using Venturi or air-compressor modi operandi); the data in Table 2 are quoted for typical mid-range flowrates of each device.