Influence of Alkalinity Enhancement with Olivine or Steel Slag on a Bacterial Community in Activated Sludge Systems

A promising strategy to mitigate Carbon dioxide emissions involves the addition of finely ground alkaline minerals to activated sludge systems. However, the release of bioactive substances from these minerals alters the microenvironment of the sludge, with the potential to induce shifts in the bacterial community. In this study, the responses of the bacterial communities in an aerobic activated sludge system to two alkaline minerals (olivine and steel slag) were investigated. This study demonstrated that the addition of olivine and steel slag to activated sludge could selectively shape the microbial community structure. The results indicated a higher diversity of the attached bacterial community in the olivine and steel slag group compared to the glass group. Olivine significantly enriched the bacterial genera that were involved in organic matter degradation and denitrification, such as SC-I-84 and Candidatus Competibacter, thereby potentially enhancing the system’s efficiency in removing carbon and nitrogen pollutants, while the steel slag promoted the growth of iron-dependent denitrifying phosphorus-accumulating bacteria including Thermomonas and Arenimonas, thus establishing a microbial consortium with the potential for nitrogen and phosphorus removal in activated sludge systems. These findings provide crucial evidence for developing mineral–microbe synergistic strategies toward carbon capture and low-carbon sewage treatment.