Resuspension traps for the removal of nutrients and algae from the sediments of shallow lakes

Purpose The effective removal of internal pollution is of great importance for lake management and eutrophication control in shallow lakes. A new technology for collecting internal pollution was tested in a shallow lake. Methods The surface sediments of shallow lakes have a low density and flow easily. Under the disturbance of wind-induced waves, such sediments will resuspend and enter the water body from the bottom of the lake and move horizontally with lake currents. Based on these characteristics, bottom traps were installed in the bottom of Lake Chaohu, China, to capture the internal pollutants in suspended sediments. Results Static water environments can be formed inside the traps. The amount of chlorophyll a and organic matter in the sediments inside the traps was approximately 3.0-4.0 times and 1.5-2.0 times greater than in the surrounding sediments, respectively. After long-term collection by traps, the average reduction of chlorophyll a, organic matter, total nitrogen, and total phosphorus in the surrounding sediments were approximately 8-14%, 9-14%, 27-48%, and 0.5-2%, respectively. A trap with a width of 4 m can collect surface sediments within a 400 m wide area (200 m on both sides of the trap). Conclusion Bottom traps can collect a large amount of surface sediment, which can be treated with desilting, which have little impact on the lake bottom ecosystem and biological community. Compared with ecological dredging, an investment of more than 50% can be saved. It has a broad application potential for the collection and removal of internal pollutants in shallow lakes.

Automated summary

Bottom traps installed in Lake Chaohu, China, effectively collect internal pollutants in suspended sediments. The traps create static water environments, leading to significant reductions in organic matter and nitrogen and phosphorus levels. This method has broad potential for removing internal pollutants in shallow lakes with minimal impact on the ecosystem.