Phosphorus removal ability of three inexpensive substrates: Physicochemical properties and application

Eutrophication of shallow freshwater lakes is a severe ecological problem all over the world. Phosphorus is one of the main triggering nutrients responsible for eutrophication of shallow freshwater lakes. Constructed wetlands provide an effective means of phosphorus removal from enriched waters. The cost of a constructed wetland depends mainly on the substrates filled within it. Here we used three inexpensive substrates including loess, cinder and limestone to construct a wetland along the shore of Lake Taihu, and then tested the total phosphorus (TP) removal ability of the wetland, the chemical and physical characteristics, and the abilities of phosphorus adsorption and inhibition of substrates. We found that the artificial wetland constructed with layered loess, cinder, and limestone but without hydrophytes and mesophytes had high phosphorus removal ability during the 44-day test, especially in the first 10 days. The average removal rate for TP was 41% for the overall testing time. Chemical properties of the substrates had stronger impacts on phosphorus removal than physical properties did. Among the three substrates, limestone had the highest phosphorus removal and inhibition ability due to its highest calcium content. This suggests that more attention should be paid to chemical composition during the selection and assembly of substrates for both constructed wetland study and its engineering applications.