# Microalgal Biomass Generation via Electroflotation: A Cost-Effective Dewaring Technology
## 5 Electroflotation-Facilitated Dewatering for Microalgal Biomass Generation
### Factors Affecting the Performance of Electroflotation-Based Microalgal Dewatering Process
#### 5.2.1 Process Conditions  
The process conditions or parameters may include current, voltage, electrolysis time, interelectrode distance, and mixing rate; for inculcation into a continuous system, flow velocity and liquid depth may be equally important. Electricity in the form of current is the driving force for electroflotation, and dictates the cathode and anode reaction rates, which in turn governs bubble evolution from the generated H\({}_{2}\) and O\({}_{2}\) gases, respectively [17; 76]. It is worth noting that, according to Equation (1), the current, voltage, and electrolysis time amongst other parameters govern energy consumption and dewatering efficiency in electroflotation. For instance, [PERSON] et al. (2017) studied the effect of the current increment on microalgae (_Scenedesmus obliquus UTEX 393_) dewatering efficiency and \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Electrolytic Technique**} & \multicolumn{2}{c}{**Reactive State of Electrodes**} & \multirow{2}{*}{**Primary Function**} \\  & **(Dominant Products or Occurrences)** & & \\ \cline{2-3}  & **Anode (+)** & & \\ \hline \multirow{2}{*}{Electrocoagulation} & Reactive & Reactive & \\  & (metal dissolution) & (reductive metal deposition) & \\ \multirow{2}{*}{Electroflotation} & Reactive & Nonreactive & \\  & (metal dissolution) & (H\({}_{2}\) formation) & \\ \multirow{2}{*}{Electrofloculation} & Nonreactive & & \\  & (O\({}_{2}\) formation) & (H\({}_{2}\) formation) & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Simplified description of the main electrolytic dewatering techniques in microalgal biomass generation. observed that in 10 min, the latter increased and reached 80% at 0.25 A, and over 90% in both 0.5 and 0.75 A supplied current. The authors explained that the increased efficiency was due to higher ion mass transport between the electrodes with the current increase [17]. Nevertheless, caution must be exercised in applying high currents as this translates to more power consumption (Equation (1)) and may lead to higher costs and energy wastage. This was illustrated in the aforementioned experiment, where approximately half the energy consumption at 0.75 A (1.516 Wh/g) was needed at 0.5 A (0.834 Wh/g) to achieve similar harvesting efficiency (\(>\)95%); 0.75 A will thus, have no added benefit to the efficiency of the process. The electrolysis time is another key variable in controlling the performance of electroflotation. For a given current supply, longer electrolysis time can lead to a dewatering efficiency of almost 100% [77], after which any additional time will ramp up the cost of the electroflotation process. For electroflotation, the required electrolysis voltage is mainly from the ohmic potential drop of the aqueous phase and it is directly proportional to the interelectrode distance. The interelectrode distance is especially important when the electrolyte conductivity is low, as higher current densities must be applied to overcome the ohmic potential drop of the aqueous phase. This inadvertently leads to a large consumption of energy [67] which is undesirable. The frequently used interelectrode distances in literature for electroflotation to generate microalgal biomass, range from 1.0 to 4.4 cm as shown in Table 6 for vertically oriented electrodes. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Micoralage**} & \multirow{2}{*}{**Predation**} & \multicolumn{5}{c}{**Electrode Characteristics**} & \multicolumn{5}{c}{**Microbial Both Conditions**} & \multicolumn{5}{c}{**Process Conditions**} & \multicolumn{2}{c}{**Performance**} & \multirow{2}{*}{**Reference**} \\ \cline{2-2} \cline{4-13}  & & \multirow{2}{*}{**Scale**} & **Anaode** & **Cathode** & **IED** & **No. ** & \multicolumn{1}{c}{**Config.