Dredging, adsorbent inactivation, and phytoremediation are commonly used to control internal nitrogen and phosphorus sediment loads in eutrophic still-water ecosystems, such as lakes and ponds. However, the effectiveness of these remediation techniques has not been verified for rivers, lakes, and reservoirs with large disturbances. In this study, a calcium-loaded clay granular adsorbent (CRB) was prepared as an alternative to commercial adsorbents, and an experiment was conducted on the ecological restoration effects of both dredging and adsorbent single treatments as well as combined treatments on eutrophic flowing water. The enhancement effect of phytoremediation on the above restoration techniques was investigated. The results indicated that CRB inactivation treatment reduced the phosphorus and turbidity of the water by 63% and 80%, respectively and increased the total nitrogen and permanganate index (COD_Mn) by 25% and 101% before phytoremediation, respectively compared to the control group. There were no significant differences in the nutrient indexes of the sediment and water between the dredging treatment and the control group, but dredging enhanced the effect of the CRB treatment. Compared with the CRB treatment, the total nitrogen and COD_Mn of water in the dredging and combined CRB treatments decreased by 13% and 15%, respectively. Phytoremediation significantly improved the effectiveness of the dredging and adsorbent treatments, both individually and in combination. Additionally, there were notable differences in the growth rates of the submerged plants and the contents of different phosphorus speciation among the plant species. Selecting suitable plant species is recommended when implementing phytoremediation methods. This study highlights that the combination of multiple restoration techniques is effective for eutrophic flowing water. The results provide a guide for the ecological restoration of flowing water.

Eutrophication of water bodies significantly accelerates water quality degradation, leading to the decline of aquatic organisms. To evaluate the synergistic restoration effects of submerged macrophyte Hydrilla verticillata and filter-feeding bivalve Anodonta woodiana on hypereutrophic water, a 40-day mesocosm simulation experiment in hypereutrophic aquatic ecosystems was conducted by setting up four treatments: control group (CK), A. woodiana group (Aw), H. verticillata group (Hv), and combined H. verticillata + A. woodiana group (HA). The results indicated that the combined application of H. verticillata and A. woodiana significantly reduced total phosphorus (TP), chlorophyll a (Chl a) concentration, and turbidity in the water, with removal rates reaching 58.3%, 60.6%, and 85.4%, respectively. The introduction of A. woodiana substantially altered the algal community composition. At the end of the experiment, the average proportion of cyanobacteria in the CK and Hv groups was 55.6%, whereas in the Aw and HA groups it decreased to 36.0%. Both total phosphorus and water-soluble phosphorus contents in H. verticillata tissues were significantly lower in HA compared to Hv, indicating that the combined treatment could reduce the risk of internal phosphorus release after H. verticillata senescence. These findings collectively demonstrate that the combination of H. verticillata and A. woodiana represents an efficient and environmentally friendly ecological restoration technology of eutrophic waters.