[Effect of Oxidation Strengthening on In-situ Phosphorus Immobilization of Calcium Hydroxide]

In this research, calcium hydroxide[Ca(OH)₂] and hydrogen peroxide (H₂O₂) were injected into the bottom mud in the form of plum blossom scatterers to investigate the effect on the control of endogenous phosphorus. The results showed that Ca(OH)₂ used singly effectively immobilized in the order of 90% of endogenous phosphorus approximately 20 mm below the sediment-water interface (SWI); however, at the same time, the anaerobic environment was enhanced, resulting in the transformation of stable phosphorus to easily released phosphorus and the accumulation of potential active phosphorus. Nevertheless, the addition of H₂O₂ greatly reduced the amount of potential active phosphorus in deep sediments after adding Ca(OH)₂. The vertical diffusion depth of Ca(OH)₂ in the sediments was significantly increased, having an influence across the depth range of 0-40mm below the SWI; the improvement at depths greater than 40 mm was not notable, which was mainly attributed to an 18-fold increase of redox potential due to the addition of the oxidant. The change of phosphorus forms in the sediment also demonstrated the excellent immobilization effect of the oxidant on phosphorus. In the 0-20 mm layer, the content of readily released phosphorus decreased significantly, while compared with a control test, Ca-P increased by approximately 10%. However, at greater depths, the amount of easily released phosphorus decreased and the rate of Ca-P increase gradually slowed.