## 1 Introduction
It is considered environmentally friendly since it does not require chemicals or significant energy input, unlike other techniques such as filtration, centrifugation, or electrophoresis. Moreover, it does not require complex equipment, making it a cost-effective and accessible option, particularly for large-scale applications. However, this method is relatively slow, with particle settling velocities averaging 0.1-2.6 cm/h, and is more effective for cells with larger dimensions [8; 42; 43]. To increase sedimentation efficiency, a preliminary flocculation process is carried out, resulting in the enlargement of settling particles. This requires the use of appropriate chemicals, such as inorganic salts Al\({}_{2}\)(SO\({}_{4}\))\({}_{3}\), AlCl\({}_{3}\), FeCl\({}_{3}\), Fe\({}_{2}\)(SO\({}_{4}\))\({}_{3}\), ZnCl\({}_{2}\), ZnSO\({}_{4}\), CaSO\({}_{4}\), CaCl\({}_{2}\), MgSO\({}_{4}\), MgCl\({}_{2}\), NH\({}_{4}\)Cl, and (NH\({}_{4}\))\({}_{2}\)SO\({}_{4}\) as indicated in studies by [8; 11; 33; 34; 35; 36; 44; 45]. Many algal strains can also undergo autofloculation, the intensity of which depends on the cultivation conditions [32; 44; 45; 46]. The mechanisms involved in this process are typically associated with the formation of positively charged bridges between cells, connected by extracellular polymeric substances (EPS). Numerous studies also indicate a correlation between the production of EPS and factors such as light intensity, temperature, pH, and the concentration of dissolved oxygen in the culture medium [44]. [PERSON] et al. [46] and [PERSON] [47] demonstrated the critical role of pH in optimizing microalgae flocculation. [PERSON] et al. [46] found that autofloculation of _Chlorella vulgaris_ began at pH 8.6, reaching over 90% efficiency at pH 10.6. Similarly, [PERSON] and [PERSON] [47] reported that adjusting _Chorella minutissima_ cultures to pH 10.5 with NaOH achieved 86.18% efficiency. This pH-induced flocculation process involves the addition of a base, such as KOH or NaOH, to elevate the pH of the algal culture. In turn, [PERSON] et al. [33] assessed the harvesting efficiency of electrocoagulation, flocculation, and pH-induced flocculation for microalgae consortium dominated by _Chlorella_ sp. grown in anaerobically digested abattoir effluent at pH values of 6.5 and 9.5. The highest biomass recovery (77%) was achieved at pH 6.5 with 0.100 g/L of aluminum sulfate after 15 min, while at pH 9.5, recovery increased significantly to 89% with a reduced concentration of 0.010 g/L after 30 min. pH-induced flocculation experiments revealed that cultures adjusted to pH 10.5 exhibited a 36% higher biomass recovery compared to those at pH 8.5 after 2 h. Authors stated that higher pH conditions (9.5) resulted in improved microalgal recovery across all dewatering systems. Similar, [PERSON] and [PERSON] [48] investigated the effect of pH on microalgae harvest efficiency, specifically for _Chlorella vulgaris_ but using Mg-sericite as a flocculant. The highest harvesting efficiency of 99 \(\pm\) 0.3% was achieved at pH 9, but efficiency decreased with further increases in pH, reaching only 92 \(\pm\) 1.3% at pH 12. The optimal pH range for harvesting was found to be 9-11, while pH below 4 resulted in less than 20% efficiency. The pH effect is attributed to the physical properties of Mg-sericite and its interactions with microalgae cells. At alkaline pH, the flocculant forms larger flocs due to increased positive charge, enhancing flocculation efficiency. Some investigators [45] suggest that the optimal pH corresponds to the pH at which the minimum flocculant dosage begins to trigger the formation of primary flocs. These studies emphasize the importance of pH control in enhancing microalgae harvesting. It is important to note that autoflocculation is also influenced by the aging effect of cells in batch cultures, where optimal conditions for sedimentation occur at the end of the exponential growth phase and during the stationary phase [49]. In turn, [PERSON] et al.