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 (MgO 2 and CaO 2) on eutrophic remediation. Results indicated that CaO 2 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 MgO 2 had a less impact on pH of the water body. Furthermore, the addition of MgO 2 and CaO 2 removed 90.31% and 93.87% of continuous external P in the overlying water respectively, while the removal of NH 4 + was 64.86% and 45.89%, and the removal of TN was 43.08% and 19.16%. The reason why the capacity on NH 4 + removal of MgO 2 was higher than that of CaO 2 is mainly that PO 4 3− and NH 4 + can be removed as struvite by MgO 2. Compared with MgO 2 , mobile P of the sediment in CaO 2 addition group was reduced obviously and converted to more stable P. Notably, the microbial community structure of sediments was optimized by MgO 2 and CaO 2 , 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, MgO 2 and CaO 2 have a promising application prospect in the field of in-situ eutrophication management. [Display omitted] • CaO 2 improved the anoxic environment of eutrophic water bodies more effectively. • MgO 2 had less effect on pH of eutrophic water bodies. • MgO 2 was better for simultaneous removal of N and P. • P fractions reshaped by CaO 2 were more stable. • Aerobic functional bacteria were increased by the addition of MgO 2 and CaO 2. [ABSTRACT FROM AUTHOR]