Cationic polymer-mediated interbacterial aggregation: A novel approach for rapid aerobic granules development

This study introduces a novel approach to aerobic granular sludge technology that minimizes the start-up time and guarantees the formation of stable granules. This is achieved by seeding the reactor with a cationic polymer without using inoculated sludge. Three cationic polymers (Hydrofloc C4400SA, C8896, and polyelectrolyte emulsion) were tested to determine the most appropriate polymer for aerobic granular sludge (AGS) startup based on the optimal dose and formation of aerobic granules. Hydrofloc cationic polymer C4400SA has excellent granule-forming properties in the AGS reactor compared to their counterparts. The formation of granules was boosted by adding 15 ppm of polymer, resulting in densely packed aerobic granules after 10 days. This improvement can be due to the more cationic properties of hydrofloc, which play a key role in bridging between cells and particles because the cationic charges of hydrofloc attract negatively charged bacteria in wastewater, thereby promoting aggregation and the formation of initial flocs. These flocs serve as the foundation for the development of granules. After 80 days of operation, 40-50% of particles with an average size range from 0.6 to 0.9 mm were observed. The AGS SBR operation was closely monitored and showed consistent efficiency in removing solids, where TP, TN, NH⁺₄ -N, and the total soluble COD were removed at average efficiencies of 62%, 73%, 97%, 93%, and 79% respectively, during steady-state cycles conducted at room temperature. Overall, this study highlights the potential of hydrofloc cationic polymer C4400SA to enhance the performance and resilience of AGS in wastewater treatment applications.