## 3 Research Results and Their Analysis
Similarly, our experiments with _Moringa oleifera_ leaf powder (0.05-0.4 g/L) and potato starch (0.02-0.12 g/L) achieved efficiencies of just 18.3% after prolonged sedimentation. The results of [PERSON] et al. [33] indicate slightly lower algae harvesting efficiencies (77-89%) compared to our findings (83.2% and 92.9%). It is important to note that they achieved the highest harvesting efficiency with a lower concentration of aluminum-based flocculant (0.01 g/L) at a pH of 9.5, suggesting that pH may significantly influence the flocculant's effectiveness. At a comparable pH of 6.5 (6.6 in our study), their highest recovery efficiency was 77% with 0.100 g/L of aluminum sulfate, which is comparable to our results, but based on maximum algae autofloculation efficiency (71.7%), i.e., without the use of a flocculant. In contrast, our study achieved harvesting efficiencies of 83.2% and 92.9%, depending on the microalgal concentration in suspension, with flocculant concentrations ranging from 0.12 to 0.17 g/L. However, it is crucial to acknowledge that [PERSON] et al. [33] examined a microalgal consortium predominantly composed of _Chlorella_ sp., while our study utilized the _Chlorella vulgaris_ BA-167 strain, which may contribute to the observed differences in the results. In comparison with other studies, such as those by [PERSON] et al. [45], our findings are generally consistent, though some differences are evident. [PERSON] et al. [45] evaluated both chitosan and aluminum sulfate across a wide range of pH values (5-9) and dosages (0.010-0.200 g/L). They optimized biomass harvesting for _Chlorella vulgaris_ using chemical flocculation followed by sedimentation, achieving very high algae harvesting efficiencies with the use of chitosan. Their optimal conditions were 0.050-0.200 g/L of aluminum sulfate at pH 9 and 0.010-0.050 g/L of chitosan at pH 5, with harvesting efficiencies ranging from 89.8% to 96.4% for aluminum sulfate and 91.2% to 99.3% for chitosan, at an initial biomass concentration of 0.335 g/L. The maximum harvesting efficiency with aluminum sulfate was about 3.5% higher than that obtained in the present study. The authors emphasized the importance of both rapid and slow mixing phases during the flocculation process, where inorganic flocculant required both phases to achieve maximum harvesting efficiency, while excessive rapid mixing with chitosan led to floc breakdown, making slow mixing the preferred method. [PERSON] et al. [45] also observed that aluminum sulfate, which primarily operates through sweep flocculation at pH 9, required higher dosages for optimal biomass recovery. Conversely, excessive concentrations of chitosan (0.050 g/L) generated a strong positive charge around the negatively charged cells, hindering aggregation due to electrostatic repulsion. This destabilized the microalgal cells, causing some biomass to float rather than settle. In a separate study, [PERSON] and [PERSON] [8] investigated the flocculation of five microalgal species, including _Chlorella vulgaris_, using aluminum sulfate and ferric chloride. They found that aluminum sulfate was more effective than ferric chloride in achieving 95% biomass removal within 62 min, particularly in a high ionic strength medium. The observed differences in algae separation efficiency results, when compared to literature data, although small, may often arise from variations in the flocculation-separation process conditions. These comparisons highlight the intricate interplay of factors such as pH, coagulant type, dosage, and mixing conditions in determining algae harvesting efficiencies. For instance, at different pH values, ions such as phosphate (PO4\({}^{3-}\)) and ammonia (NH4\({}^{+}\)) exist in varying forms within the suspension. At pH 6.5, the culture medium contains higher concentrations of NH4\({}^{+}\) and PO4\({}^{3-}\), which may compete for interactions with the coagulant and microalgal cells.