Optimizing the hydrolysis-acidification stage in municipal wastewater treatment: comparison of immobilized fillers and granular sludge

The decomposition of organic macromolecules in sewage currently benefits substantially from hydrolysis-acidification. The full use of its qualities can help domestic sewage to biodegrade more quickly, which promotes the subsequent aerobic reactions. This study evaluated the hydrolysis-acidification performance of granular sludge and filler in residential sewage. Both forms were highly effective at producing volatile fatty acids (VFAs) at the beginning of the reaction, but the granular sludge gradually disintegrated over time, particularly at low temperatures. The production of VFAs decreased (68.08 mg/L), and the effluent dissolved organic nitrogen (DON) increased (6.23 mg/L). However, the effluent of fillers remained at a lower level (1.3 mg/L) and produced more VFAs (74.13 mg/L). High-throughput sequencing revealed that the filler included a greater quantity of hydrolytic-acidifying bacteria than the granular sludge, which resulted in higher performance. In this study, the optimal form of utilizing hydrolytic acidifying bacteria was discussed to provide a theoretical basis to improve the full utilization of organic matter in domestic sewage and the removal of as much total nitrogen as possible.