Copper tailings (CTs) and orthophosphate are major environmental pollutants. CTs cause severe heavy metal pollution, and orthophosphate is one of the primary causes of water body eutrophication. This study aimed to alleviate heavy metal pollution by CTs and the eutrophication of water caused by orthophosphate. To this end, a 50 mg/L orthophosphate was used as a chemically active leaching solution and passed through a CT soil column. The tail water was then collected. Laboratory leaching tests showed that the thermally modified CTs effectively trapped orthophosphate, and the orthophosphate content in the leachate was 0.15 mg/L. After chemical washing, Cu2+, Cd2+, and Zn2+ were tested in the tail water, and the heavy metal ions in the tail water were removed using an advanced treatment technology. After treatment with 20.0 g/L water hyacinth biochar (WHBC), the removal rates (R%) of Cu2+, Cd2+, and Zn2+ were 99.48, 94.94, and 94.84%, respectively. These results demonstrated that this novel scheme for the synergistic purification of CTs and orthophosphate was feasible in the laboratory. This study provides new theoretical guidance and technical support for CT soil heavy metal remediation and water eutrophication treatment.