Enhancing wastewater remediation by drinking water treatment residual-augmented floating treatment wetlands

In this study, the involvement of aluminum-based drinking water treatment residual (DWTR) as substrate in floating treatment wetland (FTW) to enhance its treatment performance was firstly proposed and trialed. A laboratory scale DWTR-FTW fed with synthetic wastewater containing COD, nitrogen (N), phosphorus (P) and mineral salts was operated in three stages of unplanted (1-30 days), planted (31-60 days) and aerated (61-135 days) modes. The results showed that the average removal rates of COD, total nitrogen (TN), total phosphorus (TP) in stage 3 were 88%, 85%, and 90.2%, respectively, indicating the outstanding purification performance of DWTR-FTW in comparison of traditional FTWs. The embedded DWTR enriches the biomass and robustly adsorbs P, while aeration supplies sufficient dissolved oxygen for the microorganism. The results revealed that 7.022 g P was accumulated in DWTR, which is 400 times higher than that in sediment and plants during the experimental period, reflecting that DWTR adsorption is the major P removal pathway in DWTR-FTW. Overall, DWTR-FTW could significantly remove pollutants, especially P, and provide an alternative pathway to enhance purification performance of FTW.