Immobilization of Phosphorus in Sediment-Water System by Active Capping Plate Under Exogenous Phosphorus Input.

Aluminum-based P-inactivation agent (Al-PIA) is a highly effective material for phosphorus removal, which has great potential to restore eutrophic water bodies. In this study, active capping plate (ACP) was formed by mixing Al-PIA with cement and fly ash. The scour resistance coefficient of the prepared ACP was 98.01 % and the water permeability coefficient was 0.139 cm/s, which meet the requirements of strength and water permeability. Exogenous phosphorus was used as an input in the indoor dynamic experiment to examine the effectiveness of ACP capping to control phosphorus in sediment-water system. The indoor dynamic experiment lasted for 110 days. After experiment, the effect of dissolved oxygen (DO) and pH was explored, the change of phosphorus concentration in the overlying water was examined, and the changes of phosphorus in ACP and sediments were also analyzed. After ACP capping, the pH eventually maintained below 8 and was slightly higher than that of the control system. The DO concentration initially decreased, then increased, and finally remained in the range of 7 to 8 mg/L. Compared to the control system, the average reduction rates of total phosphorus (TP), dissolve total phosphorus (DTP) and dissolve inorganic phosphorus (DIP) in the overlying water were 90.57%, 91.69%, and 92.80%, respectively. ACP promotes the conversion of unstable phosphorus in sediments to stable phosphorus, and calcium-bound phosphorus (Ca-P) is the main form of phosphorus fixed by ACP. In addition, ACP was found to have a limited effect on reducing the risk of release of biologically available phosphorus from sediments. [ABSTRACT FROM AUTHOR]