Who does better for in-situ eutrophic remediation in anoxic environment improvement and nutrient removal: MgO2 versus CaO2

The long-term insufficient dissolved oxygen (DO), excessive nitrogen (N) and phosphorus (P) have become the main causes of the troublesome eutrophication. Herein, a 20-day sediment core incubation experiment was conducted to comprehensively evaluate the effects of two metal-based peroxides (MgO2 and CaO2) on eutrophic remediation. Results indicated that CaO2 addition could increase DO and ORP of the overlying water more effectively and improve the anoxic environment of the aquatic ecosystems. However, the addition of MgO2 had a less impact on pH of the water body. Furthermore, the addition of MgO2 and CaO2 removed 90.31% and 93.87% of continuous external P in the overlying water respectively, while the removal of NH4+ was 64.86% and 45.89%, and the removal of TN was 43.08% and 19.16%. The reason why the capacity on NH4+ removal of MgO2 was higher than that of CaO2 is mainly that PO43− and NH4+ can be removed as struvite by MgO2. Compared with MgO2, mobile P of the sediment in CaO2 addition group was reduced obviously and converted to more stable P. Notably, the microbial community structure of sediments was optimized by MgO2 and CaO2, which showed that the relative abundance of anaerobic bacteria decreased and that of aerobic bacteria increased significantly, especially some functional bacteria involved in the nutrient cycle. Taken together, MgO2 and CaO2 have a promising application prospect in the field of in-situ eutrophication management.