A combined application of different engineering and biological techniques to remediate a heavily polluted river

River pollution is becoming a serious problem worldwide. A field-scale experiment was undertaken to remediate a heavily polluted river using a combined engineering approach of aeration, microorganisms, biological aerated filtration, artificial biofilms and ecological floating beds. Prior to remediation, the river water was black, anoxic and highly sulfidic. With remediation, the chemical oxygen demand decreased from ∼250 to ∼50mgL−1, NH4+-N decreased from ∼27 to ∼4mgL−1, sulfide decreased from ∼3 to ∼0.3mgL−1, and total suspended solids decreased from ∼270 to ∼40mgL−1. At the same time, dissolved oxygen increased from ∼0.1 to ∼3.5mgL−1, and water clarity increased from ∼6 to ∼40cm. Furthermore, the unpleasant odor emanating from the polluted river was also stopped, and local farmers have begun using the water for irrigation. This field-scale experiment thus indicates the potential usefulness of this combined engineering approach to remediate heavily polluted rivers.