Dominant removal mechanisms of phosphorus in combined pond-wetland ecological treatment system

In order to determine the influence of environmental variations on phosphorus removal mechanisms in a combined pond-wetland system, the dominant removal mechanisms of phosphorus in different treatment unit and their influence on phosphate transformation between sediment and water column were investigated through analyzing the differences of phosphorus fractionation with water conditions. The results show that the precipitation of particulate phosphorus, the adsorption/complexation of dissolved inorganic phosphorus and the filtration of particulate phosphorus were the dominant removal mechanisms of different units in turn. Variations of dominant removal mechanisms produced there were some similarities and differences existing in sedimentary phosphorus fractionation in each unit. Additionally, it was the precipitation process of suspended phosphorus that played a relative important role in phosphorus removal in cold periods, and that was adsorption/complexation of dissolved inorganic phosphorus in warm periods. Therefore, environmental variations evidently affects the phosphorus removal performance in the ecological treatment system.